From this morning's Military.com lead story (I'll run through it with some commentary):
Army Engineers at the Picatinny Arsenal, N.J.-based Joint Service Small Arms Program office have been working for the last six years on a radical approach to ammunition and weapons that has the potential to cut the weight Soldiers carry by nearly 50 percent.A couple quick things here...According to Kori Phillips, lead engineer on the program, the JSSAP office was told by the infantry center at Benning to concentrate on the light machine gun -- in this case the SAW. So at least to some extent, the Army has telegraphed its priority as lightening the M-249 in one way or another (they recently did it with the M-240 by fielding the Mk-48).
Researchers are using so-called "cased telescoped" ammunition that does away with the propellant-holding brass shell and replaces it with a lightweight plastic case. So far the program, dubbed Lightweight Small Arms Technologies, has built three M-249 Squad Automatic Weapon-like machine guns and fired more than 10,000 of the lighter rounds with the same rate of fire and accuracy of a standard SAW.
And one other interesting thing of note is that they developed a whole new firing system for the LSAT SAW that has a rotating bolt...
The new cased telescope-firing SAW looks almost the same on the outside as its M-249 counterpart but uses a rotating action and a novel feed system that fires a standard 5.56mm ball projectile and ejects the plastic case and link from its own port.According the Phillips (and I only half understand what she's even saying) the chamber supports the entire length of the case which is "key with a polymer case. You can't have any exposed surface otherwise it will sheer." It's a straight through feed and eject and the chamber is not attached to the barrel. Also since the weapon is lighter, it has a lot more kick than a SAW. So engineers put in a "long stroke soft recoil" spring system in it, "so there's no buffer spring in the butt stock."
"One of the other things we've completely avoided in this system is the failure to feed and failure to eject," Phillips added. "In your SAW system, that's where you primarily have failures and malfunctions."
Engineers have also built a prototype M-4 that fires the lighter rounds. The experimental M-4 weighs about the same as a standard M-4 but has a 40-round magazine that's slimmer than the current one and straight instead of curved. And since half the weight of a legacy bullet is due to the brass case, a Soldier's load of more than 200 rounds in combat will drop substantially.Phillips admitted you can't shave much weight from the already pretty light M-4 system. But the unique characteristics of the ammo allow engineers to fashion a straight mag, just as long as the current one but with ten more rounds.
The M-4 variant of the cased telescope rifle has a so-called "rising chamber" action that's fed ammo from the rear -- what JSSAP engineers jokingly call a "fauxpup" after the so-called "bullpup" operating systems popular with European small arms. It looks similar to a standard M-4, but the operating system actually gives the experimental rifle an extra four inches of barrel length, Phillips said.The rifle looks almost the same as the M-4 -- no magazine behing the trigger, Stoner lovers -- but since the ammo is fed from behind the bolt, the same size gets four extra inches of reach out and touch you.
While the cased telescoped ammo is almost ready for prime time, the more exotic caseless rounds still need some work, Phillips explained. Testers are having problems keeping the rounds -- which are essentially hard, molded propellant with an embedded 5.56 mm bullet -- from degrading in high heat. They're also expensive, hard to make, and tough on the shooter.Now here's where things got dicey. The caseless ammo is just simply not there. Though it offers a huge advantage in weight and volume, the instability of the round and its expense and difficulty in manufacturing have kept it in the lab. But I've been around more than a few SAW gunners who'd take the 40 percent weight reduction over nothing any day.