At any rate, squeezing 5 or 10 percent better performance out of a weapon is nowhere near as important as making sure the weapon has ammo when it needs it. So, I wouldn’t dismiss logistical challenges as a pain we should suck up and push through.

The much-heralded 6.5 Grendel is not as good a round as everyone likes to pretend it is. It is slow, and the only benefit to slow is that it doesn’t kick a lot, meaning you can fire it full-auto.

As I’ve said before, there is no such thing as a general purpose cartridge. It doesn’t exist. If you want your infantry’s capability to reasonably extend beyond about 200 yards, then the Grendel won’t do that. The drop on the round is so great that at 600 yards you wouldn’t even be able to see your target in the scope when you fired. THat sure as hell doesn’t sound like a sniper round to me. Hell, I’d even submit that the .308 NATO is not high-enough velocity for a “really good” sniper rifle, but that is just because I’m biased to the .300 win mag for long range shooting, which acheives 3,000 fps with a 190 grain bullet.

My major quibble is that a necked down to .24 caliber .308 would not serve as a general purpose gun any better than a .308 would. It would not. Such a round is actually made. it is called the .243 Winchester. I own one that I use for deer and coyote hunting. Its kick is less than the .308, but not decidedly so — certainly not enough to make it manageable firing in full-auto, without a bipod, at least.

The fact is that, as much as it is a pain in the arse, there is no such thing as a “general purpose” round, and out military would do good to get past that line of thinking. A squad machine gun (bipod or fixed mount fired) shouldn’t be firing 55 grain .22 caliber rounds. It should be firing 150 grain 30 caliber rounds. A sub-machine gun should not be firing hypersonic 55 grain .22 rounds. It should be firing 220 grain, sub-sonic 45 caliber rounds (or even bigger). An infantry GP rifle for ranges of 200 yards or more should not be firing a 55 grain .22 round. It should be firing the same .308 rounds as the squad machine gun. An infantry-level light machine gun (shoulder fired type) is the only thing that I think you should be allowed to let fire a 55 grain .22 round, but even then, I’d push for more like a 100 grain 24 caliber round, with a lighter powder charge pushing it out to, say, a 200 to 300 yard effective range (similar to a 7.62 by 39, but with a lighter bullet and subsequent higher velocity).

I know it is a pain to supply a bunch of different ammunition to soldiers in the field, but if we really want to have as effective an infantry force as possible, I think we need to “bite the bullet” and go that route. If we could manage it in WWII, we certainly can today.

Anyway, as you note, the US Army and Marines didn’t take carbines seriously, and they actively fought the introduction of an intermediate cartridge for decades — before leaping onto the M-16 and its glorified .22, when the M-14 failed as a universal answer to the need for a battle rifle, submachine-gun, and light machine-gun, all in one.

I actually don’t think that idea is a terrible one, but a full-power .308 isn’t the way to implement it. If you neck that same cartridge down to .243 (6 mm) or .260 (6.5 mm) and put it in a slightly larger M-16 (AR-10), that gun probably can serve as a designated marksman’s rifle, a room-clearing submachine-gun, and a light machine-gun, all in one.

I do tend to believe, however, that the US Army did not consider carbines to be effective front line armament, due largely to the fact that we continued to carry high-powered rifles for the next 20 years after this report was completed, and only switched to smaller ammunition carbine type rifles upon the release of the M-16 in the 1960s.

I am a firm believer in the idea that our infantry units ought to be carrying a mixed bag of guns like they did in WWII. I know it is harder to supply ammo when there are many different types, but the benefits to having long-range high powered rifles fighting next to squad automatics for long range bullet-hose applications, fighting next to sub machine guns and machine carbines for storming close-range bullet hose purposes really lent to the diversity of an infantry unit’s capabilities.