The Corner


Today in Useless Metrics: Firearms Edition

A gun enthusiast inspects an FN Herstal rifle during the annual National Rifle Association (NRA) convention in Dallas, Texas, May 5, 2018. (Lucas Jackson/Reuters)

A Fox News headline: “US Army eyes new automatic rifle that fires with pressure equivalent to tank: report.”

I wondered a little about that: pressure?

Obviously, they couldn’t mean a rifle that fires a round with the same power — or energy, to be exact — as a tank. One of the reasons for that is that firing such a weapon would almost certainly kill or seriously injure the man firing it. Newton’s third law and all of that, which is why the scenes in movies in which people shot with hand-held firearms go flying across the room are silly: The recoil from such a powerful weapon would send the shooter flying across the room in the same way. Physics don’t play.

What the army is referring to here is the pressure inside the chamber when the round is fired, which, in the rifle in question, would indeed be on the order of what’s seen in a tank. But the projectile is a tiny fraction of that fired by a tank, which makes this comparison almost entirely useless. A Nerf ball dropped on your head from 1,000 feet falls with the same gravitational acceleration as a Steinway grand piano dropped from 1,000 feet. But it doesn’t hit as hard, as Sir Isaac Newton and Wile E. Coyote know.

The round in question is the 6.8mm Remington SPC, which already is in use among some U.S. military units. It’s also a popular hunting round, firing a bullet identical in diameter to the popular .270 Winchester, one of the most popular modern deer-hunting rounds. It’s more powerful than the current standard issue 5.56mm rifle round but considerably less powerful than many common hunting rifles, clocking in at right around half of the energy of your granddad’s old .30-06 (about 1,600 ft-lbf vs. something on the order of 3,000 ft-lbf, depending on the particular bullet).

U.S. forces have asked for a more powerful AR-type rifle because the current 5.56mm round doesn’t do as well against modern body armor and other features of the modern battlefield. The trade-off is that bigger and more powerful rifles weigh more, need bigger magazines (or magazines that need to be changed more frequently), and are more difficult to shoot well, especially for smaller soldiers.

Hunters who use AR-style rifles — and there are a lot of them — like the 6.8mm for much the same reason: The 5.56mm rifle is too small to use on larger and more dangerous game, and is in fact prohibited for that purpose — on the grounds that it is not powerful enough to be used to hunt humanely — in some states and on many private hunting reserves. In Texas, where feral-hog hunting is practically the official state sport, AR-style rifles chambered in more powerful calibers are very popular for hunting. Bill Wilson of Wilson Combat is such an avid hog-hunter that he had his company develop a powerful new semiautomatic rifle round specifically for use on pork, which some pun-happy genius in the marketing department christened the .458 HAM’R.

Gun geekery aside, there is a serious point here: The next time some would-be gun-grabber starts going on about how nobody needs a “powerful,” “military-style” rifle for hunting, you might want to remind him that many of the hunting rifles in current use are much more powerful than the rifles carried by most American soldiers — and more powerful than the new, more potent ones they are considering, too.

In the gun debate as in much else, Williamson’s First Law applies: “Everything is simple when you don’t know a f***ing thing about it.”

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