22 long rifle cartridge exterior ballistics

7/27/2019 22 Long Rifle cartridge Exterior Ballistics

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.22 Long Rifle Exterior Ballistics(from gunsmokes website)

Ever wonder what the trajectory of a 22 Long Rifle bullet looks like? I often have,

especially when trying to sight in a rifle. In this series of articles you'll find "thoughtexperiments" conducted with the help of computer software that, among its many usefulfeatures, can predict the path, or trajectory, of a bullet in flight. Covered subjects includebullet drop, wind deflection, and the effect of scope cant.

Exterior Ballistics (this page)Wind Drift: Cross WindWind Drift: Head On WindScope Cant

This page covers how bullet drop varies with distance, and attempts to shed some light onoptimum sight settings. Later I'll look at the effect of wind on bullet drift.

How far above point of aim at 25 yards would you sight in your favorite squirrel rifle to staywithin a 1" circle with a dead on hold? What would the drop be at 100 yards with thatsighting? How many rounds at the range would it take to come up with answers to thesequestions?

Take it from me, its far easier to calculate the answers with a modern computer program. Iuse Jim Ristow'sGun ControllerV2.2.7 to take a look at trajectories for Federal's

American Eagle discount load, as well as the premium UltraMatch subsonic cartridge.Here's what I found out.*

Gun Controller requires a ballistic coefficient to perform its calculations, but not one of thehalf dozen ammunition catalogs I reviewed had published that information. Fortunately,Gun Controller has the capability to determine the ballistic coefficient from range data.Federal's catalog lists velocity data for 25, 50, 75, and 100 yards, making this calculationvery easy. Table 1 below shows the trajectory results for the American Eagle bargain load,typical of most dime store 22 ammo that sells for about $2 a box. I assumed that I wasgoing after a target with a 1" diameter vital zone, and asked Gun Controller to determine

the optimum sighting in distance so that I could hold dead on the target and still hit withinthe 1" circle.
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Table 1. Trajectory of a typical 22 Long Rifle high velocity cartridge.

From looking at the table, it might surprise you to see the bullet starting off 1.5" below theline of sight, but remember that the scope is 1.5" above the center line of the rifle bore. Atabout 12 yards, the bullet crosses into the bottom of our 1" circle, and at 25 yards is .2"above the circle center. When the bullet reaches 40 yards it is at the top of the circle, and

at about 67 yards the bullet falls out the bottom of the circle. Way out at 100 yards, thebullet is about 4 3/4" low. Figure 1 shows the trajectory.


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Figure 1. Trajectory plotfor 22 Long Rifle high velocity load.

We can do the same thing for Federal's subsonic target load. Match shooters favor thisload because the turbulence that accompanies transitioning through the sound barrier isabsent.

Table 2. Trajectory of a 22 Long Rifle subsonic cartridge.


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The slightly lower velocity shifts the midpoint trajectory and circle crossing points closer tothe muzzle: 35 yards at circle top, about 57 yards at circle bottom, and .32 high at 25yards. At 100 yards, the load is down more than 7 inches. The 25 yard distance is actuallyhigher than that of the high velocity load in order to compensate for the lower velocity. Andthe range within which a dead on hold is good goes from 54 yards with the high velocityload to about 49 yards with the target fodder. At 100 yards the high velocity load is downby about 4 3/4", while the target ammo drops 7".

These figures will be close for most rifles (including 10/22 rifles) shooting high velocity andsubsonic loads. Federals velocity data was obtained with a 24" test barrel. Velocity for the22 Long Rifle peaks with barrel lengths of about 20 inches, and actually drops off withlonger or shorter barrels. Test barrels usually have chambers cut to minimum dimensions,which tend to produce slightly higher velocities than those found in sporting or even targetarms. These two factors work against each other for Federal's setup, but may not entirelyoffset each other. The difference between these calculated trajectories and those obtainedwith your rifle will, however, be fairly small.

Figure 2. Trajectory plot for 22 Long Rifle subsonic load.

The tables above also contain drift data calculated for a 15 mph wind crossing the bulletpath from the left at 90 degrees. The data also shows the lead necessary to hit a target

moving from right to left at 10 mph. Since the target is moving into the wind, the bullet pathfirst leads the target, then falls behind it as distance increases. Under these conditions, ittakes a lead of almost 4 feet to hit the target at 100 yards. Now that would be some shot!

Back to the 10/22 Index...
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22 Long Rifle Wind Drift: Cross Wind

After considering how far a 22 Long Rifle bulletdropsas distance increases, it was onlynatural to wonder how much effect wind had on group size. The ranges available here inthe San Francisco Bay Area are never calm, and even on the best days feature ten tofifteen mph breezes, with gusts up to twenty-five. Worse yet, the direction is seldomconstant, as most of the ranges are situated in canyons and hills that bend and distortwhat might otherwise be steady on-shore winds. A light 10 mph breeze doesn't feel likemuch, but best groups hovered near the half inch mark at 50 yards. No matter whatammunition or how good the trigger pull and barrel, that half inch barrier seemedunbreakable. Could such a light wind really make that much difference? It was time tobreak out Jim Ristow'sGun Controller(V2.2.8) once again to take a look at wind drift forFederal's American Eagle discount load, as well as the premium UltraMatch subsoniccartridge. Here's what I found out.

Starting with the Federal economy load and a 10 mph wind crossing from the right, Table1 shows that the deflection at 50 yards would be close to an inch. The calculationassumes that the wind is steady for the entire 50 yards, which owing to the gusty nature oflocal breezes is somewhat optimistic. But if the wind speed varied between zero and fivemph, drift would spread between zero and one inch. The best group size under suchconditions, if no allowance for wind was made, would be one inch, and would depend onthe rifle having zero deviations, and the rifleman making every shot perfectly. Figure 1shows a plot. Note that at 100 yards, deflection increases to more than 5 inches!
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Table 1. Wind Deflection of a typical 22 Long Rifle high velocity cartridge.

Figure 1. Wind Drift plot for 22 Long Rifle high velocity load.

It is starting to look like shooting sub MOA groups in conditions like this would take amiracle, no matter how well tuned the rifle, or how much magnification was available withthe scope. But maybe there is better ammunition available than the bargain stuff.


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Table 2 shows what happens when we switch to subsonic ammunition. A first guesswithout first looking at the table would be that deflection would increase, but such is notthe case.

Table 2. Wind drift of a 22 Long Rifle subsonic cartridge.

According to Jim Ristow, author of Gun Controller, deflection undergoes some unusualchanges near the speed of sound. In Jim's words: "When a 22 is fired within the"Transitional Zone" air drag is minimal until it starts exiting the "Zone". While you wouldthink there should be deflection at the start of a 22LR trajectory, physics says no 'causethe bullet is nearly being fired in a vacuum. This is why higher muzzle velocities producemore deflection and why Chuck Yeager's ride was rough when trying to get TO the speedof sound, then immediately smoothed out as he crossed it. If you consider his plane aprojectile, just accelerating rather then decelerating, you get the idea." Jim goes on to saythat most ballistics programs go bananas when asked to compute deflection for smallprojectiles traveling at speeds near the speed of sound. They predict negative deflection

(bullets deflecting up wind!), or just plain bomb. Indeed, Jim has made specialadjustments to Gun Controller to account for the phenomena. The bottom line, though, isthat the calculations are most useful for comparison between loads and condition sets,and actual deflection may differ from the calculations. In this case, deflection at 50 yardsin the same 10 mph cross wind drops by .05" for the subsonic round, a difference hardlyworth mentioning. Figure 2 shows the wind drift plot for the subsonic loading.


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Figure 2. Trajectory plot for 22 Long Rifle subsonic load.

If you're shooting a 22 long rifle in even light wind, you don't have too far to look for analibi when all your bullets don't all go into one hole. As these tables and charts show, abreeze of just 10 mph can blow your shot by an inch at 50 yards. And if you shoot invariable winds, as most of us do, a 2 MOA (1") group is the best you can hope for evenwith a rifle that shoots like a laser, unless you know how to compensate for wind drift, andconsistently judge wind speed.

22 Long Rifle Ballistics22 Long Rifle Drift: Head On Wind

22 Long Rifle Scope Cant

22 Long Rifle Wind Drift: Head On Wind

If a 10 mph cross wind can deflect a 22 Long Rifle bullet almost one inch at 50 yards,what change in impact point is due to the same velocity head on (blowing toward theshooter from the target) wind? Again, Gun Controller can help find some answers.

Table 1 shows that the bullet will hit .12" high at 50 yards. Looking back to theplots shot instill air,the impact point would be .35" high at 50 yards. That's a change of almost 1/4"! Nowonder those BR50 shooters use so many wind flags!
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Table 1. Trajectory of a typical 22 Long Rifle subsonic cartridge in head on wind.

Figure 1. Trajectory plot for 22 Long Rifle subsonic load in head on wind.

Figure 1 above tells us that the bullet drops almost 7" at 100 yards, an increase of morethan 2" over theshots made in still air.

22 Long Rifle Ballistics22 Long Rifle Drift: Cross Wind22 Long Rifle Scope Cant
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22 Long Rifle and the Effect of Scope Cant

Scope what? Scope Cant describes the tipping or tilting of the rifle and scope to one sideor the other of verticle. Very small devaitions from straight up make surprisingly largechanges to impact point. To find out just how large, I once again turned to Jim Ristow's

Gun ControllerV2.2.8.

The Exterior Ballistics portion of Gun Controller has a function that allows introduction of asight cant error. Sight cant is measured in degrees, with 6 degrees equal to the slant ofthe minute hand as it points to 12:01 on an old style analog clock. One minute of tip isn'tmuch, and it would be easy to miss it when looking through the cross hairs, especailly ifthere were no horizontal or vertical references visible. Table 1 shows that the bullet startsoff .16" to the left of the line of sight, just as you would expect if the scope was tipped tothe right. The bullet crosses the line of sight at about 30 yards, and by the time it arrives at50 yards, its 1/4" right of the aiming point.

Table 1. Trajectory of a typical 22 Long Rifle subsonic cartridge showing the effectof scope cant.

Figure 1 shows the plot of the deflection data from Table 1.
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Figure 1. Trajectory plot for 22 Long Rifle subsonic load showing the effect of

scope cant.

Back to the Ballistics Index...
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22 long rifle cartridge exterior ballistics

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