Long Range Shooting

by Fred Ray on September 23, 2006 · 0 comments

I was watching Future Weapons last night on the Discovery Channel, which had a segment on the Barrett .50 caliber sniper rifle. I’ve handled these in the military (but have not actually fired one) and they are quite impressive. Depending on whose figures you use, they have an effective range of 1500-2400 yards. The one I examined was a Marine Corps model with a 20x scope, the Army models appear to have 10x models.

Naturally this sparked a comparison with the guns of the 1860s, particularly the Whitworth. As I mentioned in a previous post, Sir Joseph Whitworth revolutionized long-range shooting in the 1850s by going to a rifle with three characteristics: a small bore (.45 caliber), a very fast twist (1:20), and a dense, heavy (530 grains) bullet with an aspect ratio of about 2½ to one. The major limiting factor was black powder, which kept muzzle velocities to just under half of what they are today. Recently historian/collector Bill Adams chronographed a repro Whitworth bullet at 1300 fps. Period shooters claimed shots at up to 2200 yards, although the sights only went up to 1200 yards. Was this possible?

Some time after the war the Army adopted the .45-70 rifle, which used a black powder center-fire cartridge. About the same time the British Army adopted the Martini-Henry, which fired a similar cartridge. The full nomenclature was .45-70-405, meaning that the bore was .45 caliber, the charge was 70 grains of powder, and the bullet weight was 405 grains using a 1:18 twist. In 1879 the Chief of Ordnance conducted a series of long-range tests at Sandy Hook, NJ. Using a more or less standard rifle they were able to hit a target at surveyed ranges of up to 3200 yards – over two miles away. Flight times exceeded 20 seconds. The best results came from using a heavier 500 grain bullet with 85 grains of powder, which must have been a bear to shoot.

Interesting to note here that the closer the Army got to Sir Joe’s formulation (.45 caliber, 500 grain bullet, 80-85 grains of powder and a fast twist), the better results they got. In fact, other than the fact that the .45-70 used a center-fire metallic cartridge, the specs for the guns were quite similar, and the claims of Whitworth marksmen shooting over 2000 yards no longer seem so outlandish.

bullets.jpg

How does that compare to today? Modern muzzle velocities run 2800-3200 fps, which does give a flatter trajectory, making range estimation less critical. An image in a very informative Wikipedia article on the .45-70 that shows graphically just what the difference in trajectory is for a .45 caliber bullet traveling at 1350 fps and a modern 7.62 bullet traveling at 2500 fps.

Barrett, in fact, is introducing a new .416 caliber cartridge for their rifles. The bullet is 2” long, which gives it an aspect ratio of almost 5:1, and it travels at an impressive 3200 fps. No word on the twist, but it still looks true to Whitworth’s principles of long-range shooting introduced some 150 years ago.


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