m4 carbine patient in german ep1998135b1.pdf

8/14/2019 M4 Carbine Patient in German EP1998135B1.pdf

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Note: Within nine months of the publication of the mention of the grant of the European patent in the European PatentBulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with theImplementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has beenpaid. (Art. 99(1) European Patent Convention).

Printed by Jouve, 75001 PARIS (FR)

(19)

EP

199

8135B1

*EP001998135B1*(11) EP 1 998 135 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention

of the grant of the patent:24.04.2013 Bulletin 2013/17

(21) Application number: 08164505.3

(22) Date of filing: 07.02.2007

(51) Int Cl.:

F41C 23/16(2006.01) F41A 5/26(2006.01)F41A 11/02(2006.01) F41A 3/66(2006.01)

F41G 1/02(2006.01) F41G 11/00(2006.01)

(54) Hand guard for a rifle

Vorderschaft fr ein Gewehr

Ft pour fusil

(84) Designated Contracting States:AT BE BG CH CY CZ DE DK EE ES FI FR GB GR

HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI

SK TR

(30) Priority: 09.02.2006 US 772494 P

(43) Date of publication of application:03.12.2008 Bulletin 2008/49

(62) Document number(s) of the earlier application(s) inaccordance with Art. 76 EPC:07866991.8 / 1 984 689

(73) Proprietor: Colt Defense LLCHartford, CT 06144-1868 (US)

(72) Inventors: Hochstrate, Paul

PLANTSVILLE, CT 06479 (US)

Robbins, Laurence

PLAINVILLE, CT CT 06062 (US)

Daigle, Arthur

PLYMOUTH, CT CT 06782 (US)

(74) Representative: Schmit, Christian Norbert MarieSCHMIT CHRETIEN

8, place du Ponceau

95000 Cergy (FR)

(56) References cited:US-A- 3 611 607 US-B1- 6 779 288

US-B2- 6 792 711


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Description

BACKGROUND

1. Field

[0001] The disclosed embodiments relate to an im-proved rifle and its law enforcement and commercial var-iances and, more particularly, to an improved military riflehaving modular subassemblies.

2. Brief Description of Earlier Developments

[0002] There are conventional firearms with an integralupper receiver and hand guard (see for instance US6,779,288 B1). The conventional firearms have a remov-able hand guard section fastened to the hand guard onthe upper receiver with screws or other similar fasteners.Field removal/reinstallation of the conventional hand

guard section hence involves removal/installation tools(for example screw drivers), and once removed themounting screws may be lost. This is not desirable inoperational conditions. Further, conventional firearmswith an upper receiver having an integral hand guard,may encumber field removal and replacement of the bar-rel. By way of example, in a conventional military rifle,for example an "M-4" type firearm having an upperreceiver with integral hand guard, the barrel nut (fasten-ing the barrel to the receiver) may be covered or "buried"within the hand guard thereby limiting accessibility to thebarrel nut. Moreover, conventional barrel nuts may havefeatures such as peripheral clearance slots, for the gastube or operating rod of an indirect gas operating system,that further impair accessibility to surface or features ofthe barrel nut engaged in order to apply tightening oruntightening torque to the barrel nut. As may be realized,rotation of the conventional barrel nut, such as at remov-al/replacement of the barrel, may involve additional un-desired disassembly of the firearm systems. By way ofexample, the gas tube, or operating rod of an indirect gasoperating system may have to be removed from the fire-arm in order to allow rotation of the barrel nut for nutremoval. In other words, the operating rod or gas tubemay have to be removed prior to barrel removal. Similarly,

on reinstallation, the barrel and at least the operating rodof the firearm indirect gas operating system, or the gastube may have to be assembled/connected to the receiv-er in sequence, rather than in unison, in order to allowrotation of the barrel nut. This is not desired. Further still,the interface between the barrel, receiver and barrel nutin conventional firearms may result in the barrel beingeccentrically positioned in an uncontrolled manner rela-tive to the mating bore of the receiver. This also is unde-sired. The exemplary embodiments disclosed hereinovercome the problems conventional firearms as will bedescribed further below.

SUMMARY OF THE EMBODIMENTS

[0003] In accordance with one exemplary embodi-ment, an indirect gas operating system for an automaticor semi-automatic firearm is provided. The indirect gasoperating system has a gas block having a cylinder. The

gas block is fitted to a barrel assembly having a bore withthe cylinder in communication with the bore. A pistonhaving a piston end and a striking end is provided withthe piston end fitted to the cylinder. A bolt assembly hav-ing a striking surface is provided. When a cartridge isfired, gas displaces the piston end and causes the strikingend to strike the striking surface displacing the bolt as-sembly. The cylinder and the piston are together remov-able as an assembly from the firearm without removal ofthe gas block.[0004] In accordance with another exemplary embod-iment, a semiautomatic or automatic rifle is provided. Therifle has a receiver having an integral hand guard port ion.

A barrel is provided having a bore, the bore removablyconnected to the receiver, the hand guard portion ex-tending over and surrounding the barrel. An indirect gasoperating system having a gas block and a piston is pro-vided with the gas block having a cylinder, the gas blockfitted to the barrel, the cylinder in communication with thebore. A piston is provided having a piston end and a strik-ing end, the piston end fitted to the cylinder. A bolt carrieris provided having a striking surface. When a cartridgeis fired, gas displaces the piston end and causes the strik-ing end to strike the striking surface displacing the boltassembly The cylinder and the piston are together re-movable as an assembly from the firearm without remov-al of the gas block.[0005] In accordance with another exemplary embod-iment, a semiautomatic or automatic rifle is provided. Therifle has a receiver having an integral hand guard port ion.A barrel is removably connected to the receiver, the handguard portion extending over and surrounding the barrel.A removable accessory device mounting rail is remova-bly connected to the receiver and having another handguard portion mateable with the integral hand guard por-tion of the receiver. A quick release lock is mounted toat least one of the removable mounting rail or the receiverfor locking the removable mounting rail to the receiver.

The quick release lock has a movable locking membermovable between a locked and unlocked positions.When in the locked position the locking member locksthe removable mounting rail in an installed position to thereceiver, and when the locking member is in the unlockedposition, the mounting rail is unlocked and freely movablerelative to the receiver. The locking member has an an-gled engagement portion protruding from the removablemounting rail and engaging a corresponding angled re-cess in the receiver. The locking member acts as a wedgein the recess with the removable accessory devicemounting rail preloaded with a biasing force against theintegral hand guard portion.[0006] In accordance with another exemplary embod-

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Provisional Patent Application 10/836,443 filed April 30,2004, United States Provisional Patent Application60/564,895 filed April 23, 2004, and United States PatentApplication 11/352,036 filed February 9, 2006. The fire-arm 30 and its sections described in greater detail belowis merely exemplary. In alternate embodiments the fire-

arm 30 may have other sections, portions or systems.Firearm 30 may have an upper receiver section 34 a bar-rel 36, gas piston system 38, and hand guard 40. In theembodiment shown, rifle 30 has receiver 34 having anintegral hand guard portion with barrel 36 removably con-nected to receiver 34. Here, the hand guard portion ex-tends over and surrounds barrel 36. As will be describedbelow, a removable accessory device mounting rail isremovably connected to the receiver and has anotherhand guard portion mateable with the integral hand guardportion of the receiver as shown here in a locked position,locked to the receiver having an integral hand guard.When in the unlocked position, the mounting rail is un-

locked and freely movable relative to the receiver. In al-ternate embodiments, the firearm may have an indirectgas operating system or gas tube operating system. Fur-ther, in alternate embodiments, the firearm may have nei-ther a piston or gas operating system and may rely onrecoil action to cycle the weapon, for example, in semi-automatic mode. Here, the gas operated linkage actuat-ing the bolt carriage in the upper receiver may be re-placed by a gas tube. Firearm 30 may incorporate stock42, lower receiver section 44, magazine well 46, clip ormagazine 48 and rear and front sights 50, 52. As will bedescribed below, upper receiver 34 having barrel 36, low-er receiver 44 and magazine well 46 are modular andconfigurable such that firearm 30 comprises a modularrifle design. In addition, lower receiver 44 and magazinewell 46 may be removable without tools or fasteners. Inalternate embodiments, more or less modules and as-semblies may be removable without tools or fasteners.As an example, magazine well 46 may be replaceableand removable such that magazine well 46 may be re-placed with a different magazine well to change caliber.Additionally, modularity with interlocking components isprovided for ease of assembly and disassembly withoutaffecting fire accuracy as well as to provide a single con-figurable firearm without having to support multiple fire-

arms. Further, the hand guard, and accessory mountingrails thereon, may be integral with the upper receiver andthe integral upper receiver, hand guard and mountingrails may be of unitary construction.[0051] Referring now to Fig. 2, there is shown an ex-ploded isometric view of the automatic firearm includingan exploded isometric view of the upper receiver withhand guard section shown in Fig. 1. As noted before,firearm 30 generally incorporates an upper receiver sec-tion 34, barrel 36, gas piston system 38, hand guard 40,rear and front sights 50, 52, ejection port cover attach-ment 54 and bolt assembly 56. Firearm 30 may incorpo-rate stock 42, lower receiver section 44, magazine well

46, clip or magazine 48 and auto sear actuator 66 as-

sembled to the bolt carrier (not shown). The barrel 36and / or the bolt / bolt carrier 56 may be coupled to upperreceiver section using conventional splined and / orthreaded / pinned locking techniques or otherwise. Handguard 40 may have features such as disclosed in UnitedStates Patents 4,663,875 and 4,536,982. Hand guard 40

has features for mounting additional devices on one ormore rails as shown and may be configured with suchrails as a "Piccatiny Rail" configuration as described inMilitary Standard 1913. The hand guard and rails maybe made from any suitable material such as hard coatanodized aluminum as an example. Hand guard 40 maybe configured for basic mission profiles or light duty railrequirements while simplifying techniques such as theGun/Light technique with firearms such as the M-4. Theperipheral devices may be devices such as sights, illu-mination devices, vision enhancing devices, launchers,laser aiming devices, Global Positioning or aiming devic-es or otherwise. In alternate embodiments, more or less

similar or different devices may be provided and more orless rail(s) may be provided. In the exemplary embodi-ment shown in fig. 2, upper receiver 34 may be of one -piece, or unitary construction incorporating integral handguard section 401 having fixed rails for example at thethree, nine and twelve oclock positions relative to thebarrel axis. In alternate embodiments, the rails may bepositioned as desired. Hand guard 40 has a removablebottom portion 60 with integral lower rail 60R for differentmounting options that may be provided. Here, removableaccessory device mounting rail 60 is removably connect-ed to the receiver with a hand guard portion mateablewith the integral hand guard portion of the receiver. Aswill be described in more detail below, removable acces-sory device mounting rail 60 has a quick release lockmounted there to. In alternate embodiments, the quickrelease lock may be mounted to the receiver. The quickrelease lock is provided for locking the removable mount-ing rail to the receiver. As will be described, the quickrelease lock has a movable locking member movablebetween locked and unlocked positions. When in thelocked position the locking member locks the removablemounting rail in an installed position to the receiver, andwhen the locking member is in the unlocked position, themounting rail is unlocked and freely movable relative to

the receiver. The locking member has an angled engage-ment portion protruding from the removable mounting railand engaging a corresponding angled recess in the re-ceiver. The locking member acts as a wedge in the recesswith the removable accessory device mounting railpreloaded with a biasing force against the integral handguard portion.[0052] In this embodiment the rail 60R may be locatedat the six (6) oclock position relative to the barrel axis,though in alternate embodiments the removable rail maybe located in any other desired location. The bottom por-tion 60 may be removable to install other accessories,such a grenade launcher as an example. The removable

bottom portion having an integral rail is mounted using a

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keyed / key way system or tongue and groove systemthat will be described in more detai l below. In the exem-plary embodiment shown in Fig. 2, support ring 62 is pro-vided at the front of the receiver 34 for strength and at-tachment purposes. Lower receiver 44 has interface 68that removably interlocks with mating interface 70 of up-

per receiver 34. Interfaces 68, 70 ma, for example, havebores and mating surfaces that lock and unlock allowingthe user to lock / assemble and unlock / disassemble thetwo assemblies, for example by the removal of pins. Inalternate embodiments, other mating and locking fea-tures could be provided, for example, mating and lockingfeatures that do not require tools. In this manner, themodular lower receiver interlocks with the modular upperreceiver and different receivers with the same interfacecan be interchanged without further disassembly. Lowerreceiver 44 has features such as trigger 72, hammer 74,fire control selector 76, auto sear 78. Lower receiver 44may have a separable or integral grip 80 and fixtures 82

for mounting stock 42. As may be realized, in alternateembodiments the upper receiver may be coupled con-ventionally to the lower receiver. Hand guard 40 (formedfor example by the joined upper and lower sections 401,60) has vent holes, integral external rails, heat shields 3,4 or double heat shields and liners (not shown) to facilitatecooling of the barrel 36 while keeping hand guard 40 ata temperature sufficiently low for an operator to hold.Removable hand guard portion 40 is show operating witha piston based operating system. In alternate embodi-ments, hand guard 40 may operate with a gas operatingsystem. Additional components may be required for agas operating system, for example, heat shields aroundthe gas tube. As noted before in this embodiment, theupper receiver 34 and hand guard 401 may be integrallyformed as a single member of unitary construction, theone piece hand guard and upper receiver unit may beformed of any suitable metal, such as steel or Al alloy,or may be formed from non-metallic material such asplastic or composites. Rails are provided on Hand guard40 and may be integrally molded. Hence, the "Piccatinyrails", hand guard and upper receiver may be integral asa one piece member of unitary construction. In alternateembodiments the rails may be removably mounted. Inalternate embodiments, more or less multiple rails may

be provided in multiple mounting locations or mountingangles on hand guard 40. The rails may be manufacturedas part of upper receiver 34 such that collimating betweenthe rail mounted device and the barrel centerline aremaintained as desired. Rails are shown as left and rightside rails for ambidextrous use. In alternate embodi-ments, rails may be mounted further forward or rearwardor at different angles. Hand guard 40 allows attachmentof a removable bottom portion 60 with lower rail 60R fordifferent mounting options that may be provided. The re-movable bottom portion 60 with rail 60R may be mountedusing a keyed / key way system or tongue and groovesystem. A heat shield may be secured to the upper por-

tion using any suitable attachment means such as

screws, pins, rivets. The bottom portion has spring load-ed movable detents that lock the bottom portion to theupper portion 6401. Accordingly, the bottom portion maybe removably attached to the upper hand guard 40I withspring loaded locks that facilitate ease of removal andreattachment of the bottom and upper hand guard por-

tions.[0053] Referring now to Fig. 3, there is shown an ex-ploded isometric view of an automatic firearm incorpo-rating features in accordance with an exemplary embod-iment. Firearm 100 is generally similar to firearm 30 inFig. 1, except as otherwise noted. Firearm 100 may havean upper receiver 104 with barrel 102 connected to upperreceiver 104 with barrel nut 146. Firearm 100 may furtherhave gas actuation system 148, lower receiver 105, handguard 108, and bolt 106. Firearm 100 may have an op-erating mechanism in the receiver having a trigger, ham-mer, and fire control selector. Firearm 100 may have amagazine well provided at the front of lower receiver 105.

In the exemplary embodiment shown hand guard 108 isprovided having an upper portion 109 and removablelower hand guard portion 110. As may be realized handguard 108 in this embodiment may be used to replace aconventional hand guard. Thus, hand guard 108 is ret-rofittable onto otherwise conventional M-4 type rifles.Firearm 100 may have features in lower receiver 105similar to the features 68 in lower receiver 44 shown infirearm 30 of Fig. 2. Upper receiver 34 may be retrofittedto firearm 100 by nature of mating features 70 interfacingwith corresponding features on lower receiver 105 offorearm 100. For example, upper receiver 34 with theunitary hand guard may fit on any M4, M16, or AR15lower receiver and be retrofittable through the entirerange. Here, upper receiver 34 and corresponding com-ponents may be provided as a conversion kit for replacingan old upper receiver. Here, the lower receiver assemblyis removably and interlockingly secured to the upper re-ceiver assembly, where the lower receiver is selectablefrom different interchangeable lower receivers each hav-ing different characteristics and each having a commoninterface to the upper receiver. As seen in Fig. 3, upperportion 109 may be clamped to firearm 100 with clampmember 114 and fasteners 116. Clamp member 114clamps upper hand guard portion 109 to barrel nut 146.

In alternate embodiments, alternate mounting tech-niques may be provided. The removable clamp portion114 provides frictional clamping with contact onto thebody of barrel nut 146 and clears the scallops on barrelnut 146. A gas tube groove is provided on upper portion120 for clearance and/or to provide positioning relativeto the receiver. The width of lower clamp member 114allows the clamp member to sit within the width of nut146 to avoid interference with the gas tube scallop r ing.Heat shields, similar to shields 3, 4 in Fig. 3, may be snapmounted or otherwise mounted to upper portion 109 and/ or lower portion 110. In this embodiment upper portion109 may for example have 9 oclock rail 124, 12 oclock

rail 120 and 3 oclock rail 122. In the exemplary embod-

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iment, lower portion 110 has 6 oclock rail 126. In alter-nate embodiments, the lower portion of the hand guardmay have more or fewer accessory device mounting rails.In the embodiment shown, no support ring is shown onupper portion 109; in alternate embodiments a front sup-port ring may be provided. Lower portion 110 is coupled

to the upper portion 109 via tongue and groove mating.Access spaces or grooves 138, 144 are provided in upperportion 109 to mate insert tongues 118 into upper rail109. Support surfaces 140, 142 engage surfaces 119and are provided to allow retention of lower portion 110by moving lower portion up (in the direction indicated byarrow Y) and then sliding lower portion 110 back (in thedirection indicated by arrow X) . In alternate embodi-ments, lower portion may be otherwise retained, for ex-ample, by sliding forward. Spring loaded latch 128 pivotson pin 516 (Fig. 29) and engages a detent or slot in theclamp 114 bottom surface. Here, Latch push pad 129 isrecessed into rail 126. Grooves 138 may be provided to

allow snap mounting of a heat shield. Here, lack of asupport ring allows a shield to extend forward so thatwhen installed front of shield becomes flush without asupport ring in the way. An upper heat shield portion maybe provided for attachment around the gas tube. Here,retrofittable rail 108 may be provided for attachment toan existing rifle. Here, a retrofittable four position rail isprovided that may be put on an existing rifle or cartridge.[0054] Referring now to Fig. 4, there is shown a sideelevation view of an ejection port cover. Referring alsoto Fig. 5, there is shown an exploded view of the ejectionport cover shown in Fig. 4. On a conventional firearm,for attachment of the ejection port door, a one piece railmay prevent sliding of pin axially due to interference fromrails. In the embodiments shown, grooves or slots 182,184 are formed on bottom of mounting lugs 166, 168. Pin158 may be provided to slide up into lugs 166, 168. Tapsor pin holes 174, 176 may be provided transverse to-wards the receiver to accept screws or pins 170, 172.Holes 174, 176 may extend through the receiver wall intothe receiver inner space. In this manner, access may beprovided to push out the pins 170, 172 into the interiorof disassembled receiver for removal. Ejection port door54 may be provided and slides over pin 158. Here, bosses166, 168 may be provided, slotted on the bottom and pin

158 may be slid in with a cross pin to hold it in place.Spring 164 and detent 156 are provided to maintain theposition of door 54 as desired. Referring now to Fig. 6,there is shown a view of a barrel extension and an ex-tractor 200. Referring also to Fig. 7, there is shown anexploded isometric view of a bolt carrier. Referring alsoto Fig. 8, there is shown another isometric view of thebolt carrier. As may be realized bolt carrier 198 holds abolt with extractor 200. As seen best in Fig. 6, in thisembodiment, barrel extension 196 has extractor lockingpin 204 provided having gap 224 between extractor lock-ing pin 204 and extractor 200. Gap 224 is shown withextractor 200 in a position without a cartridge in place.

When a cartridge is in place, gap 224 may be reduced,

such as to .005 inches nominal where extractor 200 flex-es to retain the cartridge. As seen best in Fig. 7, in theexemplary embodiment bolt carrier 198 is provided foruse with a gas piston or indirect gas operating system,as will be described below, that operates against carrierkey 210. In the exemplary embodiment, the key may be

a solid key. Pin 214 is provided with two screws 212 tohold carrier key 210 to bolt 198. In alternate embodi-ments, other attachment methods may be provided. Car-rier key has impingement face 216 to interface with theindirect gas operating systems rod. As seen best in Fig.8, skids 218, 220 are provided on the back of carrier 198.Skids 198, 220 are provided such that when bolt carrier198 is impacted by the piston of an indirect gas operatingsystem (e.g. impinging the impingement face 216 andhence impinging on the bolt carrier offset from the cen-terline of bolt carrier 198 and generating an overturningmoment causing the back end of bolt carrier 198 to kickdown), the skids provide a raised compensating surface

on the lower rear portion of bolt carrier 198 to counterthe overturning moment and distribute the loading on thebolt carrier 198 thereby allowing the bolt carrier to slidesmoothly rearwards towards the receiver extension. Re-ferring now to Figs. 9-9A, there is shown a respectivelypartial section view and partial cut away perspective viewof an upper receiver 34 and a barrel assembly in accord-ance with another exemplary embodiment. Referring al-so to Fig. 10, there is shown an exploded isometric viewof the receiver 34 and barrel assembly. Referring alsoto Fig. 11, there is shown an exploded view of a barrelextension. Referring also to Fig. 12, there is shown anexploded view of the barrel extension. Referring also toFig. 13, there is shown another isometric view of the bar-rel extension. Referring also to Fig. 14, there is shown aside view of a barrel. Referring also to Fig. 15, there isshown another side view of the barrel. Referring also toFig. 16, there is shown an isometric view of a barrel nut.[0055] Receiver 34 is substantially similar to receiver34 described previously, except as otherwise noted. Sim-ilar features are similarly numbered. Receiver 34 is, asshown in Fig. 9A, a one piece member of unitary con-struction with an integral hand guard 401. In the exem-plary embodiment shown in Figs. 9-9A, gas piston sys-tem is depicted disposed between barrel and receiver 34

for example purposes. In alternate embodiments, the fire-arm may have a gas tube in place of the gas piston sys-tem. As seen best in Figs. 9-9A, the receiver 34 has abore 226 in the barrel. Barrel assembly is received andmated to the receiver as will be further described below.In the exemplary embodiment, barrel assembly generallyincludes barrel 36, barrel extension 196 and a barrel nut238. Barrel 36 has bore 236, a breach with cartridge re-ceiving section 234 and bolt interfacing surface 228. Thebarrel extension 196 is threaded onto barrel 36 with boththreads and seating surface for positive location. In al-ternate embodiments, the barrel extension may be inter-faced with the barrel in any other manner. In alternate

embodiments, barrel extension 196 may be integrally

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formed as part of barrel 36. In alternate embodiments,bolt interfacing surface may have a different shape, suchas a cone shape or other suitable shape. Barrel extension196 is placed in bore 226 having a flange that stopsagainst a flange of bore 226. Barrel extension 196 hastaper 256 to center and lock barrel extension 196 in po-

sition and to increase the clamped surface area. The bar-rel in combination with barrel extension may be attachedto the receiver with barrel nut 238. Barrel nut 238 is pro-vided to clamp and lock barrel 36 into counter bore 226of the receiver. Barrel 36 attachment is accomplished viataper 256 on barrel extension 196. Barrel nut 238 isthreaded on the outside for engaging internal threads inbore 226. Extension flange 268 is provided on barrel nut238 and provides engagement for wrench (e.g. spannerwrench) inside bore 226 for example, the flange 268 ofthe barrel nut may be castleated as shown in Fig. 1B. Byproviding barrel nut 238 as shown, the nut 238 may beremoved or installed in the receiver 34 of unitary con-

struction with integral hand guard and without, for exam-ple, removing a gas piston operating system or a gastube. Here, for example, nut 238 has an outer circumfer-ence that clears the gas operating system G. Angled in-terior mating surface 266 {see also Fig. 16) on barrel nut238 is provided for centering of the barrel 36 via matingclamping and centering surface 256 of barrel extension196 (see also Fig. 12) . The interior of the bore 226 ofthe receiver 32A is provided with inner threads that en-gage the outer threaded barrel nut 238. As may realized,the tapered surfaces 256, 266 respectively on the barrelextension and barrel nut provide additional surface areafor frictional clamping and cooperate to centralize the bar-rel due to the matching taper on the nut and barrel. Here,the combination of barrel nut 238, extension 196 andbore 226 provides very effective locking, barrel centering,and eliminates the potential for the barrel to move relativeto the receiver as any tolerance related clearances orplay between the barrel and receiver are eliminated. Inthe exemplary embodiment, a locating notch 246 may beprovided in barrel extension 196 (see Figs. 11 and 13)for index pin 240 to positively locate the barrel 36 in theproper orientation. Barrel index pin 240 may be pressedinto bore 244 on the bottom of the upper receiver 34 fromunderneath. In this manner, a stronger interface may be

provided, for example, as pin 240 may be longer andsofter material and may be less likely to deform metal.As seen in Figs. 11-12, in the exemplary embodiment,extractor locking pin 204 may be provided, pressed intobarrel extension 196. As noted before extractor lockingpin 204 acts as a backing surface for extractor 200. Inalternate embodiments, any suitable surface may be pro-vided. Extractor locking pin 204 may be provided, for ex-ample, on any M-4 or other suitable firearm. Extractorlock pin 204 is provided in barrel extension 196 and po-sitioned to back up extractor 200. In alternate embodi-ments, extractor locking pin may be provided on any suit-able barrel. Referring also to Fig. 6, extractor 200 may

have a typical clearance 224, for example of .005". In

alternate embodiments, other suitable clearances maybe provided. Bullet casing flexure, for example in theevent of over pressure due to barrel obstruction, maymove back extractor 200 and close gap 224 to abut ex-tractor lock pin 204. In the embodiment shown, pin 204may be fixed in place and press fit into extension 196.

[0056] As will be described further, in the embodimentshown in Fig. 14, a reduced radius 260 may be providedbetween cartridge receiving section 234 and bolt inter-facing surface 228. As may be realized by comparisonwith the representative conventional barrel shown in Fig.15, in the exemplary embodiment the cartridge entryramp or chamfer 262 is eliminated and replaced with en-try radius 260 to reduce the unsupported length of a car-tridge. This reduces the chance for cartridge failure. Asnoted before, the extractor locking pin 204 effectivelylocks extractor 200 in place tending to minimize thechance of failure, for example where the cartridge de-flection under pressure would cause extractor 200 to flex

excessively resulting in a failed extraction or otherwise.To further mitigate risk of failure, radius surface 260 atthe mouth of cartridge receiving section 234 is minimized.Radius 260 is provided off face 228 of barrel 36 on theinside and rolls into chamber 234. Here, radius 260 isinterface between the inner surface of the chamber 234and face 228. Reduced radius 260 provides a sharpercorner and provides more support for the casing. In con-trast, a conventional cartridge entry ramp 262 having an-gled or cone 262 and radius 264 as shown in Fig. 15provides less cartridge support. Radius 260 reduces theempty space and provides additional backing surface forthe casing where the casing, in the region where be aweak link reducing the chance of brass failure. The weak-est part of the casing is the back area. If the casing fails,it will tend to blow out in the area around the extractordue to lack of support. In the exemplary embodiment theflexure of extractor 200, provided on the bolt (not shown)is snubbed by contact with pin 204. Here, pin 204 sup-ports the extractor 200 prevents casing failure by stop-ping extractor 200 from excessive flex. Here, the combi-nation of radius 260 and pin 204 significantly reduce thechance of such failure. In this manner, the rear of thecartridge casing that is unsupported is minimized. Radius260 may have any desired size, for example from .030

inches to .050 inches and may be polished. In alternateembodiments, radius 260 may be different. In other al-ternate embodiments, the entry surface may be generallyrounded to provide the desired support while ensuringproper feed of the cartridge into the chamber.[0057] Referring now to Fig. 17, there is shown an ex-ploded isometric view of a sight and gas piston assemblyin accordance with another exemplary embodiment. Re-ferring also to Fig. 18, there is shown a side view of asight 292 and gas piston assembly 294. Referring alsoto Fig. 19, there is shown a side view of a sight and gaspiston assembly. Referring also to Fig. 20, there is shownan exploded side view of a sight and gas piston assembly.

Referring also to Fig. 21, there is shown an exploded

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isometric view of a sight and gas piston assembly. Re-ferring also to Fig. 22, there is shown an exploded iso-metric view of a sight and gas piston assembly.[0058] Referring again to Fig. 17 there is shown a rep-resentative upper receiver assembly 296, gas piston as-sembly 294, barrel assembly 300, and lower hand guard

assembly 298. In the embodiment shown, the receiveris illustrated as being similar to receiver 34 (describedbefore) for example purposes. In alternate embodiments,the receiver may be of any suitable type. In Fig. 18, thesight assembly 292 is shown with the sight in a raised,deployed position. In Fig. 19, the sight assembly 292 isshown with the sight in a lowered, stowed position. Re-ferring now to Fig. 20, there is shown a side explodedview of the gas piston assembly 294 of the firearm. Thegas piston assembly 294 is an indirect gas operating sys-tem facilitating automatic or semi-automatic operation inplace of a conventional direct gas operating system aswill be described below. The gas piston assembly 294

may be adjustable, allowing the operator to vary gas pres-sure as desired. A suitable example of a gas regulatorfor a gas piston system is described in U.S. Patent Ap-plication Serial No. 11/231,063, filed 9/19/2005. As seenin Figs. 20-22 the firearm has a gas block 306. The gasblock 306 may be fitted, for example to the barrel assem-bly 300, (though any other suitable barrel may be used)the barrel assembly 300 has a bore (not shown), in fluidcommunication with a gas passage 403 (see Fig. 22) inthe gas block. In the exemplary embodiment, the gaspiston assembly 294 has a cylinder sleeve piston 304and a operating rod 312 is housed within the hand guardof the upper receiver. In the exemplary embodiment thegas piston assembly 294 may be installed and removedfrom the firearm as a unit as will be described furtherbelow. The cylinder sleeve is located in a bore 402 in thegas block. The piston 304 is f itted to cylinder 302. Oper-ating rod 312 is joined to the piston and interfaces withbolt carriage assembly 198 provided within the upper re-ceiver (see Figs. 7- 8). Here, the operating rod has astriking end. The bolt carriage assembly has a impinge-ment surface 216 cooperating with the rod 312 of theoperating system. When a cartridge is fired, pressurizedgas enters cylinder sleeve 302 in the gas block, displacespiston 304 and causes operating rod 312 to impinge the

impingement surface 216 displacing the bolt assembly198.[0059] Referring again to Fig. 7, the bolt carriage as-sembly 198 has a bolt carriage frame or carrier and aimpinge portion 210. Impinge portion 210 is impinged byoperating rod 312 at face or portion 216. Impinge face216 is located to be substantially coaxial with the oper-ating rod 312. The impinge portion 216 may be suitablyshaped (e.g. tapered) to direct loads imparted by rod 312into the base that engages the impinge portion to thecarrier frame. The impinge portion 210 may be press fit,keyed, pinned or otherwise fastened in any desired man-ner into its corresponding grooves of carrier 198. In al-

ternate embodiments, key ways could be provided within

the impinge portion and a corresponding interface on thecarrier. In this manner, the bolt assembly may withstandhigher impact and operating loads. Referring back toFigs. 20-22, the cylinder 302 in the gas block has port influid communication with the gas block gas passage 403through an intake or feed disposed on a surface of the

cylinder sleeve facing the bore in the gas passage. Apiston and rod assembly having a piston 304 and oper-ating rod 312 (housed within hand guard and receiverwhen mounted to the firearm) cooperate with the cylindersleeve in the gas block 306. Piston 304 is movably fittedto the cylinder sleeve 302. The operating rod 312 is fix-edly joined at its front end, for example by a threadedand/or pinned connection, to piston 304. In the exemplaryembodiment, the operating rod may be an assembly witha hollow portion, such as sleeve 310 and a solid endportion, such as rod 312. As may be realized the hollowsleeve, results in a reduction in weight of the operatingrod while increasing stiffness. The reduced weight of the

operating rod reduces the energy imparted by the oper-ating rod against the bolt carriage, while maintainingequivalent acceleration and hence travel of the bolt car-riage when impinged upon the operating rod. In alternateembodiments, other suitable assemblies may be used,for example, where the piston and rod are of two pieceor unitary construction. In this embodiment, piston 304may have a coupling section that couples with sleeve310, and operating rod 312 has a coupling section 320that accepts coupling sleeve 310. As seen in Figs. 20-21,piston 304 and rod 312 each may have a shoulder thatmates with sleeve 312. Pins 328 are provided to locksleeve 310 to piston 304 and rod 312. In alternate em-bodiments, other engagement techniques could be pro-vided such as threaded coupling. In the embodimentshown, when a cartridge is fired, pressurized gas enterscylinder sleeve 302, displaces piston 304 and causes theoperating rod 312 to impinge the impingement surface216 displacing the bolt carriage assembly. A guide maybe provided, for example, to house the operating rod al-lowing the operating rod to slide freely relative to the re-ceiver. The guide may also have a feature that mateswith a mating feature of receiver to correctly position rodrelative to the bolt carriage assembly within receiver. Thegas piston assembly also includes Spring 314 is provided

between the shoulder of rod 312 and stop washer 316to bias the rod 312 toward the cylinder sleeve 302 wherestop washer 316 abuts the receiver. As may be realized,the operating rod and piston comprises a multi piece op-erating rod in order to reduce the cost of manufacturingand also reduce weight. For example, sleeve 320 maybe made from standard tubing with reduced tolerance.Additionally, components may be heat treated. In the ex-emplary embodiment the sleeve may connect the piston304 to end portion of rod 312 with threaded connections,and pins 328 keep the threaded connections from disen-gaging. A groove 313 may be provided for a snap ringon operating rod 312. After assembly of spring 314 and

/ or stop 316, the snap ring may be added capturing the

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spring 314. In this manner, when the piston and operatingrod assembly is removed, the assembly, including thespring and retaining components is removed also withoutfurther disassembly of the firearm. The spring 314 mayalso serve as a retention member for stop washer 316during removal and insertion of the gas piston assembly.

For example the end coils of the spring may be positivelyengaged with the piston and stop washer. For example,the piston and stop washer may each be provided witha channel or groove for interlocking with end coils of thespring. In this embodiment, a snap ring would not be usedto retain spring and stop washer on the operating rod.[0060] Referring still to Figs. 21 and 22, the gas pistonassembly 294 incorporates a quick removable cylindersleeve 302. The sleeve may be removable from the frontof gas block 306 and therefore removable from the frontof the receiver or rail. This further enables removal of thegas piston assembly from the firearm as a unit. Here, thecylinder and the piston are together removable as an

assembly from the firearm without removal of the gasblock. In the exemplary embodiment removable cylindersleeve 302 is maintained captive with takedown pin 356above cylinder sleeve 302 engaging slot 342. Pin slot342 in the upper portion of cylinder 302 provides a camsurface for pin 356 to cam gas cylinder sleeve 302 toseal gas cylinder 302 opening to gas port in sight block306. In this manner, pin 356 engages takedown notch342 such that pressure reacting on cylinder 302 causespin 356 to cam cylinder 302 down to the exhaust holeand making a tighter seal. Wave spring 354 is providedunder the head of cylinder sleeve 302 to bias cylinder302 forward, removing play and actuating the cam sur-face 342 by lock pin 356. In this manner, the cylinder 302is coupled to the gas block 306 wi th removable pin 356,where pin 356 provides a camming surface to seal cyl-inder 302 to a gas port in gas block 306. The take downpin may be held captive, for example, by the spring 362and detent ball 360, or pin 358, for example. Indexing pin344 is provided for aligning purposes, aligning cylindersleeve 302 in proper angular orientation relative to gasblock 306. Index pin 344 rests against cam surface 404.Cam surface 404 cams the cylinder sleeve 302 outwards.In the exemplary embodiment cam surface 404 is angledso that rotation of the cylinder sleeve (for example, coun-

terclockwise) bears the pin 344 against cam surface 404forcing cylinder sleeve 302 out of bore 402. Here, thecylinder with index pin 344 in cooperation with cammingfeature 404 allows cylinder 302 to be rotatably positionedin gas block 306 with index pin 344 engaging cammingfeature 404 with camming feature 404 providing a cam-ming surface to extract the assembly from the gas block.In the exemplary embodiment, external annular groove(s) 340 are provided on cylinder 302 for cutting carbonbuildup in gas block bore 402 housing cylinder sleeve302 where the gas sleeve is the actual cylinder outersurface. Gas ports 303, 403 (see Fig. 22) may be pro-vided respectively in the cylinder sleeve 302 and the gas

block 306, for example gas intake port(s) to the cylinder

sleeve. The cylinder sleeve 302 may also have exhaustports 348. The annular grooves 340 in the outside diam-eter of cylinder sleeve 302 facilitate cutting gum or carbonthat may have impacted on the inside and act as a scrap-per and may also be relieved in the back to clear anycarbon buildup. Referring still to Figs 21 and 22, front

sight assembly 292 generally comprises base section408, front sight post 308 and a spring loaded pivot ordetent assembly. Front sight support 308 is mounted tobase 408 with sight pivot pin 410. Sight post 434 is thread-ed into sight support 308 and may be vertically adjustableby rotation and locked with detent 436 spring loaded byspring 438. Front sight 292 comprises a raisable sightwith a folding construction allowing a user to position thesight in a raised position shown or to rotate the sight toa lowered stowed position. Spring loaded detent ballslock the sight 308 in the raised, upper or stowed, loweredpositions. Holes 428 are provided in sight piece 308.Holes 418 are provided in sight mount 408. Holes 418

house balls 414 where balls 414 are preloaded againstsight 308 via Bellville washers 412 backed by Sight pivotpin 410. Pivot pin 410 is retained in bores 420, 430 withwashers or Bellville washers 422 and retaining ring 424.Holes 418 and 428 are provided with intentional misalign-ment between the holes or pockets 428 and holes 418housing balls 414 to allow the sight to be preloadedagainst stop surface 419 where the balls 414 do not fullyseat in pockets 428. Here, the detent bias sight step 423,425 onto flat 419 of sight frame depending on whetherthe sight is in the raised or lowered position. In alternateembodiments, any suitable stop surfaces or features maybe used. Here, sight 308 is provided with bottom locatingstep 423 preloaded against surface 419 due to thepreloaded balls being misaligned with holes 428, result-ing in a rotational moment being applied to the sight.Here, the detent bias and tends to lock the sight forwardagainst a positive stop 419. Here the detent balls beingspring loaded creates the bias. In alternate embodi-ments, more or less balls may be provided or alternatedetent mechanisms may be provided to preload the sightagainst a stop feature. Spring loaded balls 414 are en-gaged by bellville washers 412 or, for example, by a com-bination Bellville and flat washer to engage in a lockedposition providing a detent that engages sight 308 and

locks sight 308 in down and up positions. Here, whensight 308 is in the up position, sight 308 is biased forward.Here, surface 423 may be provided with a pad on thatbias in position and locks down against so that sight 308always repeats in the raised position where the raisedposition is positively located as opposed to relying solelyon the positioning of the detent alone where play may bepresent. Here, the sight is preloaded against a positivestop without any play. Here, four dimples 428 may beprovided rotated and misaligned, for example by one de-gree relative to the poles 418 in the sight 308 when in adesired position, for example, the raised position. Thismisalignment causes balls 414 to contact a side of holes

428 and opposing sides of holes 418, forcing site 308

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forward and against surface 419 where surface 423 ispreloaded against the forward portion of surface 419.Similarly, when in the lowered position, misalignmentmay cause balls 414 to contact a side of holes 428 andopposing sides of holes 418, forcing site 308 rearwardand against the rearward portion of surface 419 where

surface 425 is preloaded against surface 419. Here, thebias is provided due to the preloaded balls acting on theside of the holes resulting in the sight being maintainedin a vertical orientation, in alternate embodiments, moreor less balls or holes may be provided in alternate posi-tions. In the embodiment shown, the bias is provided bymisalignments of the holes, for example, where the holes428 in sight 308 are offset by one degree relative to holes418. In alternate embodiments other offsets or misalign-ment may be provided to obtain the desired detent. Here,the site 308 has holes 428 rotated counterclockwise rel-ative to holes 418 as shown in Fig. 24 developing a biasonto the forward portion of surface 419 and rotating the

sight forward. Similarly, when in the lowered position, therotation is opposite biasing sight 308 against the rear-ward portion of surface 419 in the stowed, lowered posi-tion.[0061] Referring now to Fig. 23, there is shown an ex-ploded isometric view of the upper receiver 34 havinghand guard portion 40. Hand guard 40 has removablelower portion 60 having heat shields 3, 4 to facilitate cool-ing of the barrel 36 while keeping hand guard 40 at atemperature sufficiently low for an operator. Guide and /or shield 472 may be provided for further cooling or as aguide for piston assembly 294. Heat shield (s) may alsobe secured to the upper portion 40 using any suitableattachment means such as pins, rivets. The bottom por-tion 60 may be removably attached to the upper handguard 40. Support ring 62 is provided at the front of thereceiver assembly 34 for strength and attachment pur-poses. Support or strengthening ring 62 of the upper por-tion of the hand guard 40 provides a more stable assem-bly to facilitate manufacture as well as provides a sectionfor the attachment of additional alternate attachmentssuch as by using mounting features 14 to couple attach-ments, such as a shoulder strap to ring 62. Hand guard40 may have features such as disclosed in United StatesPatents 4,663,875 and 4,536,982. Hand guard and re-

ceiver section may be configured as shown or otherwiseto support such rails as a "Piccatiny Rail" configurationas described in Military Standard 1913. The rails may bemade from any suitable material such as hard coat ano-dized aluminum as an example. Hand guard 40 may havea forced air cooling system as will be described. For ex-ample, radial air grooves may be provided on barrel 36that extend through the receiver section. The air groovesare part of the forced air cooling system that utilizes themotion of the bolt and bolt carriage assembly to pumpcool air along the barrel and through hand guard assem-bly which houses a radiator element that surrounds areduced diameter portion of the barrel. Here, air may be

forced from the receiver by the bolt assembly, through

the barrel retaining nut via grooves into and around theradiator and out cooling holes or slots in the hand guard.In alternate embodiments, the cooling system may beemployed on alternate firearm types. Here a one piecemonolithic upper receiver is provided having a removablebottom portion 60 of the hand guard where the portion

60 may also have an integral rail, for example, a Pickat-tiny rail. Here, the bottom portion and rail may be removedto install other accessories, for example, a grenadelauncher. Here, the rails on three sides of receiver 34 arefixed at nine oclock, twelve oclock and three oclock withthe bottom six oclock being removable, for example, toallow for mounting of additional accessories. In alternateembodiments. The lower six oclock rail may be attachedby other suitable methods, for example, by latch, rotarylatch, push pin, wedge block, front latch or otherwise. Forexample, a front latch may engage support ring 62.[0062] Referring now to Fig. 24, there is shown an ex-ploded isometric view of an upper receiver assembly.

Referring also to Fig. 25, there is shown an end view ofan upper receiver assembly. Referring also to Fig. 26,there is shown an isometric view of a removable handguard. Referring also to Fig. 27, there is shown an ex-ploded isometric view of the removable hand guardshown in Fig. 26. Referring also to Fig. 28, there is showna side view of the removable hand guard shown in Fig.26. Referring also to Fig. 29, there is shown an isometricsection view of the removable hand guard shown in Fig.26. Upper receiver with hand guard 296 is shown as amonolithic receiver with a support ring and has the sameor similar features as receiver 34 with hand guard portion40. In alternate embodiments, upper receiver 296 maybe provided with our without a support ring. Upper re-ceiver 296 is provided with rails on three sides fixed atthe nine oclock 478, twelve oclock 480 and three oclock482 positions with the bottom six oclock rail 484 beingremovable as part of lower portion 298, for example, toallow for mounting of additional accessories. Lower por-tion 298 has features the same or similar as portion 60.As shown in Fig. 25, heat shields 476, 474 may be pro-vided with attachment rivets 486, shield spacers 488 andbacking washer 490. In alternate embodiments, othersuitable shields or attachment methods may be provided.Lower hand guard section 298 is provided with a spring

loaded latch or locking member 500 that fits into and locksup into a recess on the inside of the underneath of theone piece upper receiver 296, for example, into a groove.Here, locking member 500 is spring loaded, with thespring loading biasing the locking member to the lockedposition with the locking member engaging a recess inthe receiver with a spring loaded engaging force. Refer-ring also to Fig. 29, a latch actuation lever 494 is pivotallymounted on pin 516 to lower portion 298. Here, the quickrelease lock has lever 494 pivotally mounted to the re-movable mounting rail for actuating the locking member500. Actuation lever 494 has tongue portion 522 engag-ing slot 520 of latch member 500. Latch member 500 is

spring loaded upward with springs 502 and engaged in

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622 are not through holes, removal of pins 618 may re-quire drilling. Referring also to Fig. 32, there is shown atop view of a mounting feature 614 of the firearm shownin Fig. 30. Referring also to Fig. 33, there is shown a sideview of a mounting feature 614 of the firearm shown inFig. 30. Radial grooves 640 are provided, turned into

feature 614 such that feature 614 is free to rotate withinbore 620 while still being captured with pin 618 interfacingwith groove 640. In this manner, feature 614 is able torotate in bore 620 without loosening or backing out.Mounting hole 642 is provided with flats 644 to providea mounting point for peripheral devices.[0065] Referring now to Fig. 34, there is shown a sideview of a piston 304. Piston 304 has annular grooves 336on the exterior of piston 304 that may form a labyrinthseal for trapping exhaust blow by through cylinder 302and to minimize carbon build up. Although grooves 336are shown radially cut, in alternate embodiments,grooves 336 may have any suitable shape, for example,

grooves 336 may be helically cut. Here, slots or grooves336 are adapted to remove carbon build up during oper-ation. In alternate embodiments, grooves 336 may beprovided with rings, with the rings adapted to removecarbon build up during operation. As previously dis-cussed, piston 304 is movably fitted to the cylinder 302and has shoulder 334 that acts as a stop. Threaded con-nection 326 is provided to connect piston 304 to rod 312via intermediate sleeve 310. In alternate embodiments,other suitable assemblies may be used, for example,where the piston and rod are of two piece or unitary con-struction. In this embodiment, piston 304 has a threadedsection 326 that accepts threaded sleeve 310 and oper-ating rod 312 has a threaded section 320 that acceptsthreaded sleeve 310. Piston 304 has a shoulder 650 mat-ing with sleeve 310. Pins 328 are provided to lock sleeve310 to piston 304. A cone shaped nose is provided onpiston 304.[0066] Referring now to Fig. 35, there is shown a sideview of an alternate embodiment piston 304a. Piston304a has rings 336a set in annular grooves on the exte-rior of piston 304a that may form a seal for trapping par-ticles and exhaust blow by through cylinder 302 and tominimize carbon build up. Although rings 336a are shownradially, in alternate embodiments, rings 336a may have

any suitable shape. Similar to piston 304, piston 304a ismovably fitted to the cylinder 302 and has shoulder 334athat acts as a stop. Threaded connection 326a is providedto connect piston 304a to rod 312 via intermediate sleeve310. In alternate embodiments, other suitable assem-blies may be used, for example, where the piston androd are of two piece or unitary construction. In this em-bodiment, piston 304a has a threaded section 326a thataccepts threaded sleeve 310 and operating rod 312 hasa threaded section 320 that accepts threaded sleeve 310.Piston 304a has a shoulder 650a mating with sleeve 310.Pins 328 are provided to lock sleeve 310 to piston 304a.A cone shaped nose is provided on piston 304a.[0067] Referring now to Fig. 36, there is shown an iso-

metric view of cylinder 302. Referring also to Fig. 37,there is shown a section view of cylinder 302. Cylinder302 has retention feature 342 cut as a half moon slottransverse the bore for a retention pin 356 through gasblock 306. As previously described, pin 356 is capturedand acts to retain and position cyl inder 302 in gas block

306. In the embodiment shown, annular grooves 340 areprovided on the exterior of cylinder 302 and form a lab-yrinth seal to block 306 for trapping exhaust blow by andthus minimizing carbon build up. Additionally, grooves340 facilitate removal of carbon. Although grooves 340are shown radially cut, in alternate embodiments,grooves 340 may have any suitable shape, for example,grooves 340 may be helically cut. In the embodimentshown, grooves 340 may be located on both sides of gasport or exhaust port 346, 348 on cylinder sleeve 302. Theannular grooves 340 in the outside diameter of cylinder302 facilitate cutting gum or carbon that may have im-pacted on the inside and act as a scraper and may also

be relieved in the back to clear any carbon buildup. Here,gas piston sleeve 302 is the gas cylinder.[0068] Referring now to Fig. 38, there is shown a sideview of operating rod 312. Referring also to Fig. 39, thereis shown a side view of operating rod 312. Operating rodinterfaces with hollow portion 310 (hollow tube) providedfor reducing mass and loading on bolt carriage key. Rod312 has a threaded section 320 that accepts threadedsleeve 310. Rod 312 has a shoulder 656 mating withsleeve 310. Pins 328 are provided to lock sleeve 310 torod 312. Rod 312 further has an annular or helical con-formal groove 654 adapted to accept an end turn of spring314. In this manner, when rod 312 is extracted from thefirearm, spring 314 is retained on rod 312. Diameter 666is provided to allow suitable clearance between rod 312and spring 314 so as not to impede motion of spring 314.[0069] Referring now to Fig. 40, there is shown a sec-tion view of spring backstop ring 316. Spring backstopring has face 660 seating on receiver 600 when the pistonassembly is installed. Spring backstop ring 316 is slide-able on operating rod 312 but is held in position by beinganchored to spring 314 with annular or helical groove662 in a manner similar to rod 312. Here, a spring wireturn engages the helical groove 662 in backstop ring 316an a similar manner as where the front spring 314 has a

wire turn engaged in a helical conformal groove 654 ofoperating rod 312. In this manner, when rod 312 is ex-tracted from the firearm, spring 314 is retained on rod312 and ring 316 retained on spring 314. Diameter 664is provided to allow suitable clearance between ring 316and spring 314 so as not to impede motion of spring 314.

Claims

1. A semi-automatic or automatic rifle comprising:

a receiver (296) having an integral hand guard

portion;

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a barrel (300) removably connected to the re-ceiver (296), the integral hand guard portion ex-tending over and surrounding the barrel;a removable hand guard portion (298) remova-bly connected to the receiver and having an ac-cessory device mounting rail (484), the remov-

able hand guard portion (298) being mateablewith the integral hand guard portion of the re-ceiver (296); andcharacterized in thatthe semi-automatic or au-tomatic rifle comprises a quick release lockmounted to at least one of the removable handguard portion (298) or the receiver (296) for lock-ing the accessory device mounting rail (484) tothe receiver;wherein the quick release lock has a movablelocking member (500) movable between alocked and unlocked positions, wherein when inthe locked position the locking member (500)

locks the removable hand guard portion (298)in an installed position to the receiver (296), andwhen the locking member (500) is in the un-locked position, the mounting rail (484) is un-locked and freely movable relative to the receiv-er (296), wherein the locking member has anangled engagement portion (513) protrudingfrom the removable mounting rail and engaginga corresponding angled recess (512) in the re-ceiver (296), wherein the locking member (500)acts as a wedge in the recess (512) with theremovable hand guard portion (298) preloadedwith a biasing force against the integral handguard portion.

2. The semi-automatic or automatic rifle of claim 1,wherein the locking member (500) is spring loaded,the spring loading biasing the locking member to thelocked position, and wherein the locking member en-gages the recess (512) with a spring loaded engag-ing force.

3. The semi-automatic or automatic rifle of claim 1,wherein the locking member (500) moves automat-ically to the locked position when the removable

hand guard portion (298) is located in the installedposition.

4. The semi-automatic or automatic rifle of claim 1,wherein the quick release lock has a lever (494) piv-otally mounted to the removable hand guard portion(298) for actuating the locking member (500).

5. The semi-automatic or automatic rifle of claim 4,wherein the quick release lock is included in the re-movable hand guard portion (298), and wherein theremovable hand guard portion (298) has an opening(514) for accessing and operating the lever (494).

6. The semi-automatic or automatic rifle of claim 4,wherein the lever (494) has tongue portion (522) en-gaging a slot (520) of locking member (500).

7. The semi-automatic or automatic rifle of claim 1,wherein the removable hand guard portion (298) in-

cludes two radially spaced heat shields.

8. The semi-automatic or automatic rifle of any of thepreceding claims, wherein the removable handguard portion (298) is selectable from a number ofdifferent interchangeable removable hand guards,each having a different predetermined characteris-tic.

9. The semi-automatic or automatic rifle of any of thepreceding claims, wherein the receiver (296) and re-movable hand guard portion (298) have interlockingguides (506) and guideways (508) guiding sliding

movement of the removable hand guard portion(298) relative to the receiver (296) to the installedposition, the interlocking guides (506) and grooves(508) cooperating with the locking member (500) tolock the removable hand guard portion (298) in theinstalled position to the receiver (296).

10. The semi-automatic or automatic rifle of claim 9,wherein the guideways (508) guide relative move-ment between the removable hand guard portion(298) and the receiver (296) in two directions angledrelative to each other.

11. The semi-automatic or automatic rifle of claims 3 or10, wherein the locking member (500) has a camsurface that engages a cooperating surface on thereceiver (296) to cam the locking member (500)away from the locked position when the removablehand guard portion is moved toward the installed po-sition.

12. The semi-automatic or automatic rifle of claims 9 or10, wherein movement of the locking member (500)between the locked and unlocked positions is in adirection angled relative to a guide direction defined

by the guideways (508) in which the removable handguard portion is moved in and out of the installedposition.

13. The semi-automatic or automatic rifle of any of thepreceding claims, wherein the integral hand guardportion has accessory device mounting rails (478,480, 482) located at three, twelve and nine oclockpositions with respect to a centerline of the barrel(300).

14. The semiautomatic or automatic rifle of claim 13,wherein the accessory device mounting rail (484) of

the removable hand guard portion (298) is located

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at a six oclock position.

15. The semiautomatic or automatic rifle of any of thepreceding claims, wherein the receiver (296) in-cludes a support ring (62) encircling the barrel (300)and having an attachment (14) for an accessory de-

vice, and wherein the removable hand guard portion(298) is located between a lower portion of the re-ceiver (296) and the support ring (62).

Patentansprche

1. Ein halbautomatisches oder automatisches Ge-wehr, umfassend:

ein Verschlussgehuse (296) umfassend einenintegralen Handschutzbereich;einen Gewehrlauf (300), der abnehmbar mit

dem Verschlussgehuse (296) verbunden ist,wobei sich der integrale Handschutzbereichber und um den Gewehrlauf herum erstreckt;einen abnehmbaren Handschutzbereich (298),der abnehmbar mit dem Verschlussgehuseverbunden ist, und eine zustzliche Schiene(484) zum Anbringen von Zusatzgerten um-fasst, wobei der abnehmbare Handschutzbe-reich (298) an den integralen Handschutzbe-reich des Verschlussgehuses (296) gekoppeltwerden kann; unddadurch gekennzeichnet ist, dass dieseshalbautomatische oder automatische Gewehreinen Schnellverschluss umfasst, der zumin-dest auf dem abnehmbaren Handschutzbereich(298) oder dem Verschlussgehuse (296) mon-tiert ist, um die zustzliche Schiene (484) zumAnbringen von Zusatzgerten auf dem Ver-schlussgehuse zu verriegeln;wobei der Schnellverschluss ein Riegelstck(500) umfasst, das zwischen einer verriegeltenund einer offenen Stellungen verschoben wer-den kann, wobei das Riegelstck (500), wennes sich in der verriegelten Stellung befindet, denabnehmbaren Handschutzbereich (298) in einer

eingebauten Stellung auf dem Verschlussge-huse (296) verriegelt, und die Gerteeinbau-schiene (484), wenn sich das Riegelstck (500)in der offenen Stellung befindet, im Verhltniszum Verschlussgehuse (296) offen und frei be-weglich ist, und das Riegelstck ein abgewin-keltes Raststck (513) umfasst, das aus der ab-nehmbaren Einbauschiene hervorsteht, und ineine entsprechend abgewinkelte Vertiefung(512) im Verschlussgehuse (296) eingreift, wo-bei das Riegelstck (500) in der Vertiefung (512)mit dem abnehmbaren Handschutzbereich(298) als Klemme fungiert, der mit einer be-

stimmten Spannkraft am integralen Hand-

schutzbereich vorgespannt ist.

2. Halbautomatisches oder automatisches Gewehrnach Anspruch 1, bei dem das Riegelstck (500) fe-dergespannt ist, und die Federspannung das Rie-gelstck in die verriegelte Stellung drckt, und bei

dem das Riegelstck mit einer federgespannten Ein-rastkraft in die Vertiefung (512) einrastet.

3. Halbautomatisches oder automatisches Gewehrnach Anspruch 1, bei dem sich das Riegelstck (500)automatisch in die verriegelte Stellung bewegt, wennsich der abnehmbare Handschutzbereich (298) inder eingebauten Stellung befindet.

4. Halbautomatisches oder automatisches Gewehrnach Anspruch 1, bei dem der Schnellverschluss ei-nen Hebel (494) umfasst, der schwenkbar auf demabnehmbaren Handschutzbereich (298) angeordnet

ist, um das Riegelstck (500) zu bettigen.

5. Halbautomatisches oder automatisches Gewehrnach Anspruch 4, bei dem der Schnellverschluss inden abnehmbaren Handschutzbereich (298) inte-griert ist, und bei dem der abnehmbare Handschutz-bereich (298) ber eine ffnung (514) verfgt, umden Hebel (494) zu erreichen und zu bettigen.

6. Halbautomatisches oder automatisches Gewehrnach Anspruch 4, bei dem der Hebel (494) einenzungenfrmigen Abschnitt (522) umfasst, der in eineNut (520) des Riegelstcks (500) eingreift.

7. Halbautomatisches oder automatisches Gewehrnach Anspruch 1, bei dem der abnehmbare Hand-schutzbereich (298) zwei radial angeordnete Hitze-schilder umfasst.

8. Halbautomatisches oder automatisches Gewehrnach irgendeinem der vorherigen Ansprche, beidem der abnehmbare Handschutzbereich (298) auseiner bestimmten Anzahl an verschiedenen ab-nehmbaren Handschutzbereichen ausgewhlt wer-den kann, wobei jeder dieser Bereiche unterschied-

liche Merkmale aufzuweisen hat.

9. Halbautomatisches oder automatisches Gewehrnach irgendeinem der vorherigen Ansprche, beidem das Verschlussgehuse (296) und der abnehm-bare Handschutzbereich (298) ineinandergreifendeFhrungen (506) und Fhrungsbahnen (508) umfas-sen, die die Schiebebewegung des abnehmbarenHandschutzbereiches (298) in Bezug auf das Ver-schlussgehuse (296) in die eingebaute Stellungfhren, wobei die ineinandergreifenden Fhrungen(506) und Nuten (508) mit dem Riegelstck (500)zusammenwirken, um den abnehmbaren Hand-

schutzbereich (298) in der eingebauten Stellung am

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Verschlussgehuse (296) zu verriegeln.

10. Halbautomatisches oder automatisches Gewehrnach Anspruch 9, bei dem die Fhrungsbahnen(508) die Bewegung zwischen dem abnehmbarenHandschutzbereich (298) und dem Verschlussge-

huse (296) zueinander in zwei Richtungen fhren,die in einem Winkel zueinander stehen.

11. Halbautomatisches oder automatisches Gewehrnach Anspruch 3 oder 10, bei dem das Riegelstck(500) eine Nockenlaufflche aufweist, die mit einerentsprechenden Gegenflche auf dem Verschluss-gehuse (296) zusammenwirkt, um das Riegelstck(500) aus der verriegelten Stellung zu bringen, wennder abnehmbare Handschutzbereich in Richtung dereingebauten Stellung bewegt wird.

12. Halbautomatisches oder automatisches Gewehr

nach Anspruch 9 oder 10, bei dem die Bewegungdes Riegelstcks (500) zwischen der offenen undder verriegelten Stellung in eine Richtung erfolgt, diein Bezug zu einer Fhrungsrichtung, die von der Fh-rungsbahn (508) definiert wird, abgewinkelt ist, inder der abnehmbare Handschutzbereich in die undaus der eingebauten Stellung bewegt wird.

13. Halbautomatisches oder automatisches Gewehrnach irgendeinem der vorherigen Ansprche, beidem der integrale Handschutzbereich zustzlicheGerteeinbauschienen (478, 480, 482) umfasst, diebei drei, zwlf und neun Uhr in Bezug zu einer ge-dachten Mittellinie des Gewehrlaufes (300) angeord-net sind.

14. Halbautomatisches oder automatisches Gewehrnach Anspruch 13, bei dem bei dem die zustzlicheGerteeinbauschiene (484) des abnehmbarenHandschutzbereiches (298) in der sechs Uhr Posi-tion angeordnet ist.

15. Halbautomatisches oder automatisches Gewehrnach irgendeinem der vorherigen Ansprche, beidem das Verschlussgehuse (296) einen Haltering

(62) umfasst, der den Gewehrlauf (300) umgibt undeine Befestigung (14) fr ein Zusatzgert umfasst,und bei dem sich der abnehmbare Handschutzbe-reich (298) zwischen einem unteren Abschnitt desVerschlussgehuses (296) und dem Haltering (62)befindet.

Revendications

1. Fusil semi-automatique ou automatiquecomprenant :

un rcepteur (296) comportant une partie int-

gre de garde-main ;un canon (300) reli de manire amovible aurcepteur (296), la partie intgre de garde-main intgral stendant au-dessus de et entou-rant le canon ;une partie amovible (298) de garde-main relie

de manire amovible au rcepteur et compor-tant un rail (484) de montage de dispositif ac-cessoire, la partie amovible (298) de garde-mainpouvant tre connecte avec la partie intgrede garde-main du rcepteur (296) ; etcaractris en ce que le fusil semi-automati-que ou automatique comprend un verrou lib-ration rapide mont sur au moins un lmentparmi la partie amovible (298) de garde-main oule rcepteur (296) pour verrouiller le rail (484)de montage de dispositif accessoire sur lercepteur ;dans lequel le verrou libration rapide possde

un lment (500) de verrouillage mobile pouvanttre dplac entre des positions verrouille etnon verrouille, dans lequel, lorsquil se trouvedans la position verrouille, llment (500) deverrouillage verrouille la partie amovible (298)de garde-main dans une position installe surle rcepteur (296), et lorsque llment (500) deverrouillage se trouve dans la position dver-rouille, le rail (484) de montage est dverrouillet peut tre dplac librement par rapport aurcepteur (296), dans lequel llment de ver-rouillage comporte une partie (513) dengage-ment incline dpassant du rail de montageamovible et sengageant dans un videment in-clin (512) correspondant dans le rcepteur(296), dans lequel llment (500) de verrouilla-ge agit comme une cale dans lvidement (512)avec la partie amovible (298) de garde-main pr-contrainte avec une force de pousse contre lapartie intgre de garde-main.

2. Fusil semi-automatique ou automatique selon la re-vendication 1, dans lequel llment (500) de ver-rouillage est soumis laction dun ressort, la pres-sion par ressort sollicitant llment de verrouillage

vers la position verrouille, et dans lequel llmentde verrouillage sengage dans lvidement (512)avec une force dengagement charge par ressort.

3. Fusil semi-automatique ou automatique selon la re-vendication 1, dans lequel llment (500) de ver-rouillage se dplace automatiquement vers la posi-tion verrouille lorsque la partie amovible (298) degarde-main est situe dans la position installe.

4. Fusil semi-automatique ou automatique selon la re-vendication 1, dans lequel le verrou libration ra-pide possde un levier (494) mont de manire pi-

votante sur la partie amovible (298) de garde-main

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pour actionner llment (500) de verrouillage.

5. Fusil semi-automatique ou automatique selon la re-vendication 4, dans lequel le verrou libration ra-pide est inclus dans la partie amovible (298) de gar-de-main, et dans lequel la partie amovible (298) de

garde-main possde une ouverture (514) pour ac-cder au levier (494) et lactionner.

6. Fusil semi-automatique ou automatique selon la re-vendication 4, dans lequel le levier (494) possdeune partie (522) en languette sengageant avec unefente (520) de llment (500) de verrouillage.

7. Fusil semi-automatique ou automatique selon la re-vendication 1, dans lequel la partie amovible (298)de garde-main comprend deux boucliers thermiquesespacs radialement.

8. Fusil semi-automatique ou automatique selon lunequelconque des revendications prcdentes, danslequel la partie amovible (298) de garde-main peuttre slectionne parmi un nombre de diffrents gar-de-mains amovibles interchangeables, ayant cha-cun une caractristique prdfinie diffrente.

9. Fusil semi-automatique ou automatique selon lunequelconque des revendications prcdentes, danslequel le rcepteur (296) et la partie amovible (298)de garde-main possdent des guides (506) dinter-verrouillage et des glissires (508) guidant le mou-vement de coulissement de la partie amovible (298)de garde-main par rapport au rcepteur (296) versla position installe, les guides (506) dinterver-rouillage et les glissires (508) cooprant avec ll-ment (500) de verrouillage pour verrouiller la partieamovible (298) de garde-main dans la position ins-talle sur le rcepteur (296).

10. Fusil semi-automatique ou automatique selon la re-vendication 9, dans lequel les glissires (508) gui-dent le mouvement relatif entre la partie amovible(298) de garde-main et le rcepteur (296) dans deuxdirections inclines lune par rapport lautre.

11. Fusil semi-automatique ou automatique selon la re-vendication 3 ou 10, dans lequel llment (500) deverrouillage possde une surface de came qui sen-gage avec une surface cooprante sur le rcepteur(296) pour sortir llment (500) de verrouillage dela position verrouille lorsque la partie amovible degarde-main est dplace vers la position installe.

12. Fusil semi-automatique ou automatique selon la re-vendication 9 ou 10, dans lequel le mouvement dellment (500) de verrouillage entre les positionsverrouille et non verrouille est effectu dans une

direction incline par rapport une direction de gui-

dage dfinie par les glissires (508) dans lesquellesla partie amovible de garde-main est dplace verset depuis la position installe.

13. Fusil semi-automatique ou automatique selon lunequelconque des revendications prcdentes, dans

lequel la partie intgre de garde-main possde desrails (478, 480, 482) de montage de dispositif acces-soire situs aux positions trois, douze et neuf heurespar rapport un axe du canon (300).

14. Fusil semi-automatique ou automatique selon la re-vendication 13, dans lequel le rail (484) de montagede dispositif accessoire de la partie amovible (298)de garde-main est situe la position six heures.

15. Fusil semi-automatique ou automatique selon lunequelconque des revendications prcdentes, danslequel le rcepteur (296) comprend une bague (62)

de soutien encerclant le canon (300) et comportantune fixation (14) pour un dispositif accessoire, etdans lequel la partie amovible (298) de garde-mainest situe entre une partie infrieure du rcepteur(296) et la bague (62) de soutien.

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the readers convenience only. It does not form part of the European

patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be

excluded and the EPO disclaims all l iability in this regard.

Patent documents cited in the description

US 6779288 B1 [0002] US 5726377 A [0050] US 5760328 A [0050] US 4658702 A [0050] US 4433610 A [0050] US 10836443 B [0050]

US 60564895 B [0050] US 11352036 B [0050] US 4663875 A [0051] [0061] US 4536982 A [0051] [0061] US 23106305 A [0058]

m4 carbine patient in german ep1998135b1.pdf

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