When you look at the soldier’s load, ammo is a natural place to consider weight reductions. Less weight means more ammo. To deal with ammo weight, we can make the bullets smaller, or change their composition. We’ve tried Caseless Ammo, and that proved to have some significant technical challenges. What if we kept the case, but made it from something else?
Enter the LSAT project.
The idea behind LSAT was to create lighter cartridges using polymer cases and telescoped1 cartridge construction, and compare those to using caseless ammo based on the G-11 project. Of course, polymer isn’t brass, and this presents some design challenges. With a brass case, you can make a sturdy rim2 that an extractor claw can grab. You can then pull the case, spent or live, out of the chamber. This doesn’t work for polymer cases. A polymer rim of similar design isn’t strong enough for an extractor claw to pull the round out. You can only push the polymer case, which makes ejection a challenge.
To deal with this problem, the LSAT light machine gun uses a swinging chamber. When the chamber swings down to feed a round, the previous round is pushed forward into the ejection chute. The chamber then swings up to interface with the barrel for firing.
The focus of LSAT was a Light Machine Gun first setup, since the current US Army LMG, the M249, is considerably heavier than an M4. There’s more weight savings to be had there. The end result was a weapon prototype that weighed 9.4 lbs for the polymer-cased telescoped ammo version3. The version firing caseless ammo weighed a little more because of the need for extra components to provide an adequate chamber seal. Polymer-cased telescoped ammo is 40% lighter and takes up 12% less volume than conventional brass-cased ammo, so a belt of 100 rounds of 5.56 mm LSAT ammo weighs about 2 pounds, rather than the roughly 3.3 lbs for a 100 round belt of 5.56 mm NATO.
Let’s briefly talk about the LSAT rifle before getting into some analysis. The LSAT rifle is much less further along designwise than the LSAT LMG. Much of this is due to the fact that the US Army’s existing rifle, the M4, is already really lightweight. It’s an excellent weapon, and weight savings from ammo changes will be less noticeable with a 30 round magazine than with a 100 or 200 round belt. Further weight savings here are likely going to require materials changes.
Recently, the LSAT program started looking at the development of 6.5 mm cased telescoped ammunition, and weapons to fire them.
And now for the breakdown. First, I like the idea of continuing research into small arms development. And I like the idea of trying to keep it evolutionary rather than trying to force a revolution like with Project SPIW or the OICW. I like the LSAT LMG and the 5.56 mm LSAT round best. I’m a big fan of weight reduction, and the weight reduction in both weapon and ammo weight are big wins for the infantryman. I also like that combination for really only having one variable being played with. We’re still using the same 5.56 mm rounds, with the 5.56 mm bullets that we know, but we’re trying to use new materials to reduce the weight burden.
I’m also fine with the 5.56 mm LSAT rifle being put on the back burner. Weight savings from lighter bullets is less attractive here because we’re dealing with significantly fewer bullets. Plus, we already have a solid, lightweight rifle. Weight reductions there are probably going to come from rifle materials, not bullet design. I’m also ok with having a different round for the belt-fed infantry support weapons and the carbines. Linked and loose ammo are basically two different things anyway.
What about the new 6.5 mm projects? That really depends on the goal of those projects. If they’re looking to replace 7.62 mm NATO with a 6.5 mm LSAT round, I’d be okay with that. Or at least, I’d be fine with looking into that and testing the daylights out of that concept. And I would also be fine with a DMR-type ‘heavy rifle’ that fired the same round, in the same vein as the Dragunov rifle.
I would not be happy with any kind of effort to switch the general issue carbine from 5.56 mm anything to 6.5 mm anything. I do not approve of the extra load. I do not approve of adding a whole bunch of extra range that the average grunt can’t use. I do not approve of ignoring a mountain of historical evidence across multiple wars that most infantry combat occurs at relatively short ranges of less than 300 meters. I do not approve of excessively optimizing to fight in Afghanistan. I do not approve of small arms solutions to problems of rules of engagement and airspace deconfliction. I do not approve of any deviation from the classic solution to the sniper problem of mortars and artillery and airstrikes.
Any effort to make the standard infantry rifle a morbidly obese4 affair with a fat, overly energetic cartridge is a return to 1950s US Army Ordnance Department thinking. That nonsense brought us the M-14, which is a piece of junk. Let’s not make the same mistakes of the past. History teaches us what our parents and grandparents did wrong so we can make our own mistakes, not steal theirs.
I’m happy to debate the merits of a different cartridge for the medium/general purpose machine gun role, but that’s a very separate question. And trying for a ‘single cartridge’ means compromising too many ways. Since the SCHV rounds are the least bad present compromise, I’m happy to try out polymer cased telescoped rounds there, where at least the projectile itself can be kept constant.
- Telescoped like the 40mm CTAS rounds, but way smaller of course. ↩
- Even on ‘rimless’ cases like 7.62 NATO. ↩
- This unloaded weapon weight is very nearly replicated in 5.56 mm NATO caliber by the Knights Armament Stoner 96 LMG. ↩
- Projected weight for an empty, opticless 6.5 mm LSAT ‘carbine’ is 8 lbs, which is about 33% heavier than an empty, opticless M4 carbine. It would make a good DMR. ↩