Army demonstrates new LSAT lightweight machine gun

The Army recently conducted a new demonstration of the lightweight machine gun from the Lightweight Small Arms Technology program (LSAT), according to a Research, Development, and Engineering Command press release.

 

The LSAT program has been run out of the Armaments Reserach, Development, and Engineering Center (ARDEC) at Picatinny Arsenal for several years. It's original goal was to produce a lightweight machine gun aimed at the M249 Squad Automatic Weapon role, by redesigning both weapon and ammunition from the ground up.  The program was later restructured to look at lightweight small arms technology applications in multiple roles, to include carbines, using the lightweight LMG as the technology demonstrator.

The M249 SAW weighs in at about 17 lbs, and the 600 round basic load of 5.56mm ammo weighs roughly the same amount, meaning the SAW gunner is the most burdened guy in the rifle squad (one of the reasons for the USMC Infantry Automatic Rifle program).  But getting weigh out of a weapon alone -- like the Marine IAR -- doesn't gain you a whole lot when most of the weight is in the ammo.  Lighter ammo is a difficult problem, because plastic-cased ammunition in conventional configurations tends to overheat, cook off, and melt to the sides of the weapon chamber when the weapon runs hot.  LMGs run very hot at high rates of fire, which is why they are usually designed with replaceable barrels, which the M27 IAR is not.

LSAT Ammo. CT above; caseless below.LSAT works around that by designing a purpose-built weapon around purpose-built 5.56mm ammo.  There are two type of ammo in development: a plastic cased case-telescoped (CT) ammunition (case-telescoped meaning the bullet is fully seated within the propellant, resulting in a cylindrical round), and a cylindrical caseless (CL) ammunition.  The LMG weapon comes in at 8.3 lbs, with 12 lbs of ammo, resulting in a 40% weight savings for the basic CT ammo; and a 50% weight savings with CL ammo.  It meets or exceeds the range, accuracy, rate of fire, and reliability of the M249 SAW.

The CT ammo is relatively straightforward; the trick to using plastic cases is a special rotating chamber design that dumps heat to keep the chamber from overheating and melting cases, plus a single-direction feed and eject, which eliminates failure-to-eject malfunctions.  The rounds use the same bullets as traditional ammo so terminal performance is the same (and can easily use M855A1 projectiles in 5.56mm configuration). 

Caseless is a lot tougher.  Though successfully demonstrated in the early 1990s during the Advanced Combat Rifle experiment with the HK G11 weapon, much of the basic formula for the CL ammo was lost when the experiment ended -- not because the CL ammo performed poorly; quite the opposite in fact.  But the G11 was a complex weapon designed for hyperburst fire, and was far to complex and expensive to field, plus hyperburst did not prove to be particularly effective.  So the caseless baby got thrown out with the G11 bathwater, and LSAT has had to reverse engineer the CL ammo formula.

I was involved with LSAT at two prior points in my career, and there was a lot of discussion about what that weight savings might mean.  A lot of soldiers indicated that given a lighter weapon and ammo, they'd just carry more ammo.  Ultimately, though, weight is currency -- you use it to trade for other capabilities.  That might be more ammo, but it might also be the ability to carry tougher body armor, better radios, specialty night vision or comms gear, or just plain be able to maneuver faster.

One of the weight trades we looked at was trading up for weapons capability.  By using LSAT technology, we once estimated that you could build a weapon with the range and lethality of a 7.62mm rifle, but with the weapon and ammo weight of the current M4 and conventional 5.56mm ammo, by using a 6.5mm LSAT carbine. Throw in M855A1 technology in your 6.5mm projectile and you're really cooking with gas.

LSAT has been on the slow boat, though, because there hasn't been a strong requirements push for it.  The conventional small arms community opposes it because it isn't conventional, and it isn't what every commercial gun manufacturer is producing for sale right now.  The ammunition community is afraid of the large bill to retool the industrial base to make CT or CL ammo (which is not too bad for CT, but significantly expensive for CL).  So LSAT struggles to find friends.

But in my opinion, screw the Army's new carbine competition -- it won't find any significantly better performance than the current M4.  Investment in LSAT, however, is the leap the Army has been looking for in small arms, becuase that weight savings really opens up the options for improving the individual soldier's performance in non-traditional ways.

Comments

[mintukumar]

Hi
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