How to adjust and modify the

Air Arms S300 & S310

S300 Tining Guide

WARNING

Important

This guide is for owners who wish to dismantle their airguns and are reasonably good with hand tools. If after looking through this guide you don't feel competent enough to attempt the job, then have your gunsmith service/tune it for you. Reading through a few times will help you get the basic procedure. Needless to say that any work carried out by individuals will void any current guarantee. This should only be carried out if really necessary with the correct fitting tools. A spring compressor should be considered essential for safety reasons and certainly makes life easier. No responsibility can be taken by the author for any work carried out. Note that a spring compressor is not required for pre charged air guns.

© JANUARY 2003.

NO PART OF THIS PUBLICATION MAY BE REPRODUCED WITHOUT PERMISSION OF THE AUTHOR.

MAKE SURE GUN IS NOT COCKED BEFORE COMMENCING WORK. EVEN THEN THE SPRING IS STILL UNDER TENSION, SO BE CAREFUL.

THERE IS A LIMIT TO THE POWER OF AIRGUNS IN THE U.K. THESE ARE RESTRICTED TO 12ft. Ibs. FOR AIR RIFLES AND 6ft. Ibs. FOR AIR PISTOLS. GUNS EXCEEDING THESE FIGURES WILL REQUIRE THE OWNER TO OBTAIN A FIREARMS CERTIFICATE BEFORE CONVERTING AIRGUNS *OVER THE LIMITS STATED ABOVE.

*This is only allowed by a registered firearms dealer.

AIRGUNS WILL GENERALLY PERFORM BETTER AFTER RUNNING IN.

IF YOUR GUN IS CLOSE TO THE ABOVE LIMITS, THEN HAVING YOUR GUN CHECKED REGULARLY CAN ENSURE THAT THE POWER HAS NOT SLIPPED OVER THE U.K. LIMIT.

For Tuning Spring Airguns See the Airgun Tuning Manual by Gremlin.

S300 Tuning Guide

The following is reproduced from the Air Arms Users Handbook. Reproduce with the kind permission of Air Arms

The air cylinder is a highly pressurised unit and must not be modified or machined in any way. Do not attempt to pressurise if there are any large surface abrasions or dents. Do not store the rifle in places subject to excessive heat. Do not attempt to dismantle when pressurised, severe personal injury may result. Do not pressurise beyond the stated maximum filling pressure, and only use clean filtered compressed air. Never use any other gas particularly industrial or welding gases such as Oxygen, Carbon Dioxide, Acetylene, Hydrogen, Nitrogen, Argon, etc.

Important Information Do not store the rifle in a damp place such as a garden shed or garage. Do not store the rifle in a plastic or PVC type gun bag. Never leave it in a cocked condition.

If there is a requirement to check the trigger adjustment it is possible to test fire this rifle without a pellet in the barrel. Usual safety precautions.

General Maintenance Regularly check the tightness of all fixings. Do not over-tighten. Some parts are made of Aluminium, stripped threads will result from over-tightening.

General Lubrication Regularly apply a few drops of gun oil to the loading bolt. It is essential to wipe over the external surfaces of the rifle with a soft oily rag to maintain the high surface finish. Failure to do this will result in surface corrosion. Regular internal lubrication is not necessary. A small amount of grease is applied on assembly. Re-lubrication will be unnecessary for a considerable time. If the operation of the rifle becomes rough, stiff or noisy this could be an indication that lubrication is required and should be investigated. Silicone oil should never be used on moving parts.

Do not allow excess lubricant to penetrate to the S340 striker rod as this will effect the consistency. It is advisable to have this rifle serviced by Air Arms or a competent gunsmith. The frequency of services is determined by the regularity of use but in all cases should be at least once a year.

Operating instructions. To cock the rifle hold securely in one hand and with the other turn the loading bolt and pull backwards until first restriction is felt, pull back again until trigger mechanism engages. Insert the pellet into the loading groove. Push the bolt forward and turn to lock. The rifle is now cocked and loaded and must be treated with caution.

The Series S300 has been designed to be totally ambidextrous and can be changed from right hand to left hand operation without the need to purchase any special parts. However the mechanism needs to be completely disassembled to enable conversion. This should only be undertaken by Air Arms or a competent Gun smith.

S300 Tuning Guide

The following is reproduced from the Air Arms Users Handbook. Reproduce with the kind permission of Air Arms

FILLING INSTRUCTIONS FROM COMPRESSOR

1. RIFLE MUST BE IN THE COCKED POSITION PRIOR TO FILLING.

2. UNSCREW END CAP FROM FRONT END OF RIFLE.

3. CONNECT RIFLE A TO COMRESSOR CONNECTION B.(SEE ILLUSTRATION) BY SCREW HOSE TO RIFLE.

4. CHECK BLEED VALVE I IN CLOSED POSITION BY ROTATING IN A CLOCKWISE MOTION.

5. SWITCH ON COMPRESSOR AT POSITION 2.WHEN GAUGE 3 SHOWS PRESSURE OF 190 BAR. SWITCH OFF COMPRESSOR.

6. OPEN BLEED VALVE.

7. DISCONNECT RIFLE BY UNSCREWING HOSE FROM RIFLE.

8. PLACE END CAP ON RIFLE.

FILLING INSTRUCTIONS FROM AIR CYLINDER 1. RIFLE MUST BE IN COCKED POSITION PRIOR TO

FILLING THE RIFLE.

2. UNSCREW END CAP FROM FRONT END OF RIFLE.

3. CONNECT RIFLE B TO BOTTLE CONNECTION A.

4. CHECK BLEED VALVE 1 ON BOTTLE VALVE IN CLOSED POSITION BY ROTATING IN CLOCKWISE MOTION.

5. SLOWLY OPEN MAIN VALVE 2 BY ROTATING IN AN ANTI-CLOCKWISE MOTION, UNTIL THE REQUIRED PRESSURE OF 190 BAR IS SHOWING ON THE GAUGE 3.

THEN CLOSE MAIN VALVE 3 BY ROTATING IN A CLOCKWISE MOTION.

6. ROTATE BLEED VALVE 1 IN CLOCKWISE MOTION TO RELEASE AIR FROM CIRCUIT.

7. UNSCREW HOSB CONNECTOR A TO RELEASE RIFLE FROM AIR CYLINDER.

8. REPLACE END CAP ON TO RIFLE.

S300 Tuning Guide

The following is reproduced from the Air Arms Users Handbook. Reproduce with the kind permission of Air Arms

Trigger Adjustment The trigger is a two stage trigger with adjustments on both stages. Be aware that adjustment to one screw will effect the adjustment of the other and the trigger will only work properly if there is the correct balance between the two. If you have no experience in adjusting two stage triggers seek guidance or leave the trigger as set by the factory.

INCORRECT ADJUSTMENT CAN MAKE THE RIFLE UNSAFE.

There are three adjusting screws. The weight of the pull screw (A) is under the front of the trigger guard. Clockwise movement increases the weight of pull. The other adjusting screws are in the trigger blade. Screw (B) adjusts the exact pull-off point Clockwise decreases the pull-off point. Clockwise decreases the pull-off point. Screw (C) adjusts the length of first stage travel. Again clockwise decreases the length of first stage travel. Remember that small adjustments will make noticeable change to the operation of the trigger.

A C B

S300 Tuning Guide

Reproduced with kind permission of Air Aims.

S300 Tuning Guide

SERIES 300 PARTS LIST

5300 BOLT HOUSING S350 5301 BOLT HOUSING FIXING SCREW S355 5302 TRANSFER PORT ADJUSTER S360 5303 TRANSFER PORT LOCK SCREW & S370

POT LOCK SCREW

5305 VALVE BODY S380 5306 SPRING FIRING VALVE S390 5307 SCREW AIR METERING S391 5310 STRIKER BODY S392 5311 CHASSIS BOX SCREW S400A 5312 CHASSIS BLOCK S400B 5315 TRIGGER GUARD S405 5316 TRIG GUARD FIX SCREW frt S410 5317 TRIG GUARD FIX SCREW rear S420 5318 WEIGHT ADJ SCREW trigger S42I 5319 WEIGHT ADJ SPRING trigger S422 5320 TOP SEAR S425 5321 TRIGGER STOP PIN S427 5322 CHASSIS FIX SCREW SHORT S430 5323 BODY LOCATION SCREW S435 5324 CHASSIS PLATE SCREW S440 5325 BOTTOM SEAR S450 5326 CHASSIS PINS LONG S455 5327 CHASSIS PINS SHORT S456 5328 CHASSIS PIN O-RING LARGE S456A 5329 CHASSIS PIN O-RING SMALL S459 5330 STRIKER • S460 5331 MAIN SPRING S461 5335 CYLINDER TUBE S465 5336 CYLINDER TUBE O-RING S470 S340 STRIKER GUIDE ROD S475 S345 SLEEVE S480

LOADING BOLT ASSY LOADING BOLT SCREW POT FIRING VALVE ASSY

BRIDGE CLAMP FILLING VALVE BODY SPRING FILLING VALVE CIRCLIP FILLING VALVE BARREL 5.5MM .22 CALIBRE BARREL 4.5MM .177 CALIBRE BARREL FIXING SCREW END CAP TRIGGER BLADE TRIGGER ADJ. SCREW NYLON LOCKING PAD" BOLT HANDING PIN BOLT HOUSING/BODY SEAL CHASSIS COVER PLATE BARREL/BOLT HOUSING SEAL FILLING VALVE STOCK STOCK SCREW FRONT STOCK SCREW REAR STOCK SCREW WASHER MUZZLE END MODERATOR MODERATOR SCREW BONDED SEAL MALE SNAP CONNECTOR CAP RETAINING RING CAP

S300 Tuning Guide

Important Notes A spring compressor is obviously not required for the Air Arms S300 precharged models

but caution is still required as the cylinder is [charged with very highly compressed air of around 180 bar (around 2646 psi. The pressure listed on the instruction sheet with each gun I should never be exceeded Read the Guide thoroughly before attempting to dismantle the gun. This may prevent you from l taking apart assemblies that you don't need to. And should make it easier. You do not need to release any air from the cylinder unless you intend to replace

the valves or strip down the reservoir. Keep lubricants out of reservoir by degreasing / cleaning any new parts. Solvents should not be used on the exhaust valve which may dissolve the plastic seal

Remove the front stock and the rear stock screw as shown in Figs. 1 and 2. Place the parts in a suitable container. This will allow the stock to be eased from the mechanism. Try to keep the mechanism square as they are a fairly tight fit.

Fig. 1.

Fig 2

S300 Tuning Guide

Do not lose the small steel washer between the front stock screw and the bridge clamp. Remove the six Allen cap head screws on the rear bolt housing, see fig. 4.

Removing the trigger guard (not required for tuning). To remove the trigger guard undo the front and rear Allen screws. Note A shows the

Fig. 3 front Allen screw being removed. The trigger unit is still held to the housing by two Allen screws, one on the inside rear, see note B. and one on the outside note C. When you remove the trigger guard don't lose the small spring that goes between the trigger guard and trigger unit. This small spring has to be replaced when the gun is assembled.

Note. A.

Fig. 4.

Note. C.

S300 Tuning Guide

After you have removed the the top screws in fig. 4. the rear holding bolt can be removed from the rear of the cylinder as shown in fig. 5.

Fig 5 Remove the Allen cap screw as shown in fig. 6. The top bolt housing and barrel can then be lifted away from the cylinder, see fig. 7. . Then the rear striker body can be removed.

Fig. 6.

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S300 Tuning Guide

This will then allow the hammer spring and hammer to be removed as shown in fig. 8. Fitting a stronger hammer spring will speed up

Fig 7 the lock time. This does not normally result in the gun giving a lot more power but the gun should be checked after any adjustments just to make sure it does not go over the legal limit.

Fig. 8.

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S300 Tuning Guide

Hammer and hammer spring being withdrawn from the rear of striker guide rod fig. 9. Please note that the hammer has a slot at the rear, this Fig. 9. slot has to be lined up with the trigger sear when it is assembled. Also the trigger may have

to be pulled when assembling the striker body. Danger. Make sure there is no Compressed air left inside the reservoir before you strip down the * reservoir. The valve body can be unscrewed from the reservoir (do not grip in a vice). ;When the valve body has been removed it is then possible to remove the exhaust valve and spring. Before you undo the brass nut (pot), the locking grub screw has to be slackened as

shown in fig. 10. The brass nut has an air flow restrictor which might have to be undone or removed if the gun is not producing enough power or you are putting it on FAC. This is the Fig. 10. small grub screw shown in fig. 10. Leaving the brass pot undone slightly will also give more power, so long as there is still enough spring pressure to hold the exhaust valve shut.

If you are putting the gun on FAC then do not ~ set the power too high. Normal waisted pellets cannot take too much power before the accuracy goes off. We have found the best FAC power to be around 18-22 ft. Ibs. This will also give more shots than if the gun was set any higher.

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S300 tuning Guide

After the locking grub screw has been slackened the brass valve retainer (pot) can be undone as shown in fig. 11.

Fig. 11. Fig. 12. shows the exhaust valve and spring removed. The internals have to be kept scrupulously clean to prevent leakage. Lubricants must not be allowed in the inside of the reservoir or on the internal parts that are under air pressure. Only high pressure lubricants are permissible in tiny quantities. Molycote 33 can help if there is any need for a lubricant. When fitting any new or used parts make sure there is no lubricant that can get inside.

Fig. 12.

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Fig. 13. Shows the exhaust valve and spring. The barrel is removed by undoing the two grub screws on the top of the bolt housing. See fig. 14.

S300 Tuning Guide

Fig. 13.

Fig. 14.

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S300 Tuning Guide

Fig. 15. shows the barrel removed. There is an O ring seal left in the bolt housing. This can be pushed out from the front with a suitable probe.

FiS 15 Fig. 16. shows the method of removing the muzzle weight or silencer. This is just held on by a small grub screw.

Fig. 16

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S300 Tuning Guide

An Allen bolt prevents the pellet bolt from being withdrawn. If you want to remove the pellet bolt then unscrew the Allen screw on the

Fig 17 underside as shown in fig. 17. When the Allen screw has been removed then the pellet bolt, the bolt can be withdrawn rearward. • If you need to look at the trigger then the side plate is held on by two slotted screws. Remove both screws as shown in fig. 18.

Fig. It.

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S300 Tuning Guide

Fig. 19. shows the trigger parts and their orientation. Inlet Valve. Fig. 19. Danger. Make sure there is no Compressed air left

inside the reservoir before you strip down the reservoir. If you need to remove the inlet valve for any reason then you will have to make a tool to remove the front filling valve body. You start by drilling the large clearance hole for the filling thread as shown in fig. 20. The filling valve body has two holes drilled either side of the filling hose thread (1/8 bsp). Drill the

First small hole and place a pointed piece of silver steel in the tool. A smaller piece of silver steel is placed in the opposite side to mark the tool pin position as seen in fig. 20

.

Fig. 20.

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S300 Tuning Guide

After marking a radius, centre punch exactly opposite the first hole, as shown in fig. 21. Drill this second hole fig. 22, and fit the second

Fig -21. pin.

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S300 Tuning Guide

The tool can then be used to remove the filling valve body. The filling valve body is being removed in fig. 23.

Fig. 23. When you have removed the filling valve body it is then possible to remove the inlet valve, you will need a fine pair of circlip pliers. The circlip is squeezed inwards and pulled out. See fig. 24. Fig. 25. shows the inlet valve removed. Do not remove valves just to see how it works, it is best done only when they are suspected of leaking.

Fig. 25. ?

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S300 Tuning Guide

Fig. 26. Shows the method of changing the bolt from right hand to left hand. It is just a matter removing the pin from one hole and replacing it in the opposite one.

Assembly of the S300 is basically the reverse of the dismantling process, but pay particular attention to the small spring that goes between the trigger guard and trigger unit if you removed it.. And don't forget to replace the washer between the stock and mechanism. See page 8. To speed up the lock time it is possible to use a slightly stronger hammer spring, see kit. This can give a faster hammer action (lock time) but can also increase the power, see previous mention on page 10. The power limit in the UK is 12 ft. Ibs. so it is important not to exceed this level if the gun is not on FAC. To lower or increase the power of the S300 first remove the small locking grub screw, this will then allow you to adjust the

small master adjusting grub screw. Unscrew a little at a time to give a small increase in power or screw in to lower power and keep the faster lock time. Avoid hitting the exhaust valve too hard, as excessive striking could bend the exhaust valve. The exhaust valve is stronger than most Precharged so this should not be such a problem. The transfer port is partially blocked by this small grub screw, restricting the airflow. After any adjustments it is important to check the power on a chronograph to make sure it does not exceed the legal limit if you do not own a FAC. Note the UK limit is 12-ft. Ibs. Important:

If power is found to be low, then check that the transfer port has not been blocked by the O ring that is fitted between the barrel and reservoir. I To remove the pellet bolt, turn the housing onto the scope rails, this will give access to the Alien screw on the underside. Fig. 27. J Note for all guns fitted with a silencer. If you ever find that the accuracy has gone or you cannot zero your scope, it is worth trying the gun without the silencer.lt has been found that in half the cases mentioned above, it was found that it was the silencer off centre.

Fig. 27.

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