Topic of the Month

A frequent question the concerned shooter asks is, "What is the maximum range for my gun?" It is not just a curiosity question, but one that can invoke serious safety ramifications as well. If you are shooting on a certified gun range, where adequate backstops are provided, this question might not be so important. However, when hunting or shooting in open country it is important to know just where your bullet may land.

For small-arms this has been a difficult question to answer. An artillery shell, because of its large size, makes a big, easily observed splash or crater when it lands. The small-arms bullet, which has a very low velocity at the end of its maximum trajectory, drops to the ground or water surface with little observable disturbance. Also, there is enough difference in distance, between succeeding shots fired with identical elevation and azimuth, that it is difficult to position an observer within sight of all falling bullets. One way to overcome this problem is to fire a prolonged burst from a machine gun and have an observer watch for falling bullets. This was the way the actual maximum range of the .30-06 Service bullet was determined.

It is well known that a projectile, fired in a vacuum (absence of air), will attain its maximum range when fired at a 45° angle. At this angle of fire the maximum vacuum range only depends on the projectile's muzzle velocity. A good approximation of the projectile's maximum vacuum range, in yards, can be calculated by dividing the velocity by 10 and squaring the results. For example, a projectile moving at 2,700 fps muzzle velocity would travel 72,900 yards or about 41.5 miles in a vacuum. For the Service Cal. .30 M2 this is about 22 times as far as it would actually travel in the air. There is no satisfactory formula for working out maximum range in an atmosphere environment. Manufacturer's charts and military data are the best source for information.

With the small-arms bullet, the effect of air resistance is so great that the maximum range is obtained at an elevation of about 29°. There is little change as the gun is elevated to about 35°. At angles greater than 35° the bullet will begin to fall closer to the shooter. This question was presented in the British Textbook of Small Arms, 1929, in which a chart of the trajectories is presented for the boat-tail Swiss bullet of approximately .30 caliber, weighing 174 grs., and with a ballistic coefficient of .284 and a muzzle velocity of 2600 fps. This chart is presented below in Table I.

Elevation (deg.)	Range (yds.)	Flight Time (sec.)	Final Velocity (f.p.s.)	Angle of Fall (deg.)
5	2464	7.56	588	11.25
10	3273	12.65	447	24.1
20	4097	20.95	390	47.68
30	4413	27.91	405	62.40
34	4455	30.2	416	66.15
35	4456	31.06	417	67.4
40	4413	34.01	429	71.35

The table shows that the bullet attains its maximum range of 4457 yards at an angle of departure of a little over 34° . At angles greater than this, the range decreases.

Heavy bullets from low-velocity, large caliber rifles will travel about 15% to 20% of their theoretical vacuum range when fired in the air. The lower the velocity and the higher the ballistic coefficient of the projectile, the closer the projectile will approach its vacuum range. Modern hunting rifles, with their relatively light weight bullets and high velocity will only obtain approximately 4% to 10% of their theoretical maximum vacuum range when fired in air.

A number of small-arms cartridges, essentially military ones, have had their maximum range in air determined by actual tests. The results of these tests are shown below in Table II.

CALIBER AND BULLET	BULLET WEIGHT (GRS.)	MUZZLE VELOCITY (F.P.S)	BALLISTIC COEFF.	MAX. RANGE (YARDS)	MAX. RANGE (MILES)
.22 LR (SV)	40	1145	.128	1500	.85
.22 LR (HV)	40	1335	.128	1565	.89
.380 ACP	95	970	.08	1089	.62
.45 ACP PISTOL	234	820	.16	1640	.93
.30 CARBINE	111	1970	.179	2200	1.25
.30 BALL M2	152	2800	.40	3500	1.99
.30 BT M1	172	2600	.56	5500	3.12
.30-40 KRAG	220	2000	.34	4050	2.30
.50 AP M2	718	2840	.84	7275	4.13

The warning often printed on the .22 LR high velocity ammunition box, states that the maximum range of the ammunition is one mile, be careful. If you look at Table II this is a pretty accurate statement. The measured distance is 0.89 miles. In the same manner, the popular .30-06 M2 shows a range of about two miles. For any bullet of similar power or less, we can use this figure and feel pretty safe about it. Most cartridges have not been tested for maximum range, but a little careful thought about those that have been, will yield a rough estimate for the others.

Round balls have a much smaller ballistic coefficient than pointed bullets and therefore the range of shot fired from shotguns is much smaller than the rifle bullets. The Ordnance Technical Manual 9-1990 gives the following distances for shot when fired in full choke shotguns: No. 00 Buckshot, 600 yds.; No. 8 shot, 230 yds.;and No. 9 shot, 210 yds. This manual also gives a formula called "Journee's Formula" for determining the approximate maximum ranges for shotguns. This formula states that the maximum range, in yards, is roughly 2200 times the shot diameter, in inches.

It is the responsibility of every hunter, shooter, or anyone else who owns a gun to have an idea of how far his bullet may travel if he misses his target. You may never know who is a mile or two down range. Life is precious, so let us always play it safe.

Topic of the Month: May 2001