June 11, 2021: For about a decade the U.S. Marine Corps and U.S. Army have been seeking caseless ammunition or polymer (instead of brass) cased ammunition that would work reliably in combat and be much (30-37 percent) lighter than conventional 5.56mm ammo using a brass case. A popular caseless variant was CTA (Cased Telescoped ammunition) in which a polymer (a form of rugged heat-resistant plastic) case contained both the bullet and the propellant. Then there was an alternative conventional design using a 30 percent lighter (than brass) polymer case. All three designs have been tested extensively during the last decade and found acceptable. The problem was that the last of these alternatives to prove acceptable was the one using polymer casings instead of brass. These rounds were 30 percent lighter than conventional rounds and while these rounds took up more space than caseless or CTA rounds, they could be used in existing weapons.

The advantages of polymer cases presented a problem, and a major one at that. Using caseless or CTA ammo meant designing new weapons and magazines to carry the shorter ammo. Conventional ammo designs successfully using polymer casings showed unexpectedly after acceptable caseless and CTA designs were tempting the military to proceed with this new ammo that replaced a lot of existing weapons.

True Velocity, the firm that developed acceptable polymer cases teamed up with a major defense firm (General Dynamics) to provide a more acceptable ammo for U.S. Army’s new LSAT (Lightweight Small Arms Technology) 5.56mm machine-gun as well as all existing assault rifles, pistols and machine-guns. That is very tempting to the army and marines, which could have the benefits of lightweight ammo without having to replace all existing rifles and machine-guns. There would still be a future for caseless/CTA ammo, but those designs would enter service more slowly.

The basic design of LSAT was available since 2012 but acceptance for production was delayed by efforts to see if it should be built to use either conventional (brass) or caseless/CTA ammo. Initially LSAT prototypes were built to test two types of lightweight ammo and it wasn’t until now that one of those lightweight ammo designs reached the point where it was ready for combat testing. That was when the True Velocity polymer case design finally arrived. Commercial ammo using the True Velocity polymer rounds were revealed in 2020, aimed at hunters and target shooters. One market that is not pleased is reloaders, who build their own ammo, often with custom propellant loads, using the reusable brass casings. For the military that is not a problem and the fact that the polymer case, unlike the brass case, insulates the rifle from the heat of the propellant is a bonus. For machine-guns that is a major advantage and military ammo is rarely reloaded. Civilian target shooters will find the heat handling aspects of the polymer case useful if they fire a lot of rounds on the range and have to be careful about overheating of the receiver (where the ammo is ignited and the empty case ejected while another is loaded). Overheated receivers are sometimes a problem with military weapons, where the heat can rise to levels where rounds fire spontaneously when loaded and before the trigger is pulled.

The LSAT machine-gun weighs 4.27 kg (9.4 pounds) compared to 8 kg for the current M249. Moreover, caseless ammo for the new machine-gun is 37 percent lighter as well. A LSAT with 1,000 rounds of caseless ammo, weighs 13.9 kg (30.6 pounds), which is 40 percent less than an M249 with a thousand rounds. Moreover, caseless ammo takes up twelve percent less space. Developers are working on caseless 5.56mm ammo that is even more compact. Unfortunately, the lighter weight, and initial higher cost of caseless ammo will take longer to gain wide acceptance because of the more compatible polymer case ammo design.

Caseless ammo is not a new concept but you need the right materials and right design to make it work. It’s all a matter of getting the right tech and the right design. Back in the 1980s German firm Dynamit Nobel developed a 4.73mm round that weighed much less than the existing 5.56mm rounds but was similar in effectiveness. The new (at the time) G11 assault rifle was designed to fire the caseless 4.73mm round. A G11, along with 510 rounds, weighed the same (7.36 kg/16.2 pounds) as an M-16 with 240 rounds (eight, 30 round magazines.) The West German army tested the G11 extensively in the late 1980s and was considering adopting it and its caseless ammo to replace its 7.62mm assault rifles. But then the Cold War ended, Germany was united, and the decision was made to go with the cheaper G36 5.56mm weapon firing conventional brass cased ammo. Caseless ammo was also more expensive than the conventional 5.56mm stuff, and there were still concerns about reliability, even after years of testing. Not much work was done on this caseless ammo in the 1990s but after 2001 American firms began working on upgrading and improving the Dynamit Nobel tech. While field testing has shown that the new polymer case design is safe and reliable, the new caseless design has to survive combat testing and the military has yet to decide on when and where to carry that out.

The U.S. Army came up with a radical new LSAT machine-gun design in 2006, mainly to save weight. The army was making an effort to reduce the load the infantry carry into combat. In both Iraq and Afghanistan infantry did most of the fighting, and the troops are using the Internet to hammer the senior commanders and politicians about the excessive loads they have to carry.

In the beginning the army called together some of its small arms manufacturers, gave them some money, and told them to come up with a much lighter 5.56mm light machine-gun. In effect, replace the M249 with the LSAT. “Start from scratch” the weapons wonks were told. The only constant was the caliber of the weapon (5.56mm) and the troop handling of the LSAT should be roughly the same as the M249. The goal was to greatly reduce the 17.41 kg (38.3 pounds) the M249, and 600 rounds of ammo, weighs. This is what a machine-gun armed soldier usually has to carry into combat.

Starting in 2008 the LSAT was quickly developed, built, and tested. LSAT passed its first field tests in 2012 which involved having eight prototypes firing 25,000 rounds over three weeks. At that point everyone agreed that it works. More testing was required to ensure ruggedness and reliability. That took five years, about twice as long as expected.

The LSAT prototypes came in two versions. One used ammo with a telescoped case, and the other was caseless. The telescoped ammo was ready for use first while the caseless stuff was still in development. Both LSAT weapons feature a revolutionary ammo feed that employs a pivot, rather than a bolt, to load the ammo into the chamber. This design propels the case out the front of the weapon. Naturally the caseless ammo has no case to eject. The use of the pivot reduced overheating problems, which are more of a hassle with the polymer case of the telescoped cartridge prototype. The telescoped case is a straight case, like a pistol round, not a bottleneck case more common with high powered rifles. A caseless round is the ideal solution but this design was more difficult to manufacture. Caseless rounds have been developed before but were found to be more expensive and more vulnerable to rough handling.

The original LSAT expectation was that if the caseless round were used, the LSAT and 600 rounds would be 9 kg (19.9 pounds) lighter than the current M249 and its ammo. The new plastic case and the LSAT is 6.8 kg (15 pounds) less than the M249.

In early 2012 eight LSAT machine-guns and 100,000 rounds of the telescoped ammo were delivered for army troops to actually use and passed field tests. At this point it became possible to use the same technology for a new assault rifle. While LSAT passed muster with the troops and the realities of use in a combat zone, by 2012 most of the fighting was over. The new machine-gun would be much appreciated by infantry operating in Afghanistan, where the machine-gunner is often lugging his weapon and all that ammo up steep hills. But back home there was less enthusiasm, and money, for a new generation of assault rifle and light machine-gun. The polymer case conventional ammo is easier to implement, especially if hunters and sport shooters continue to report success with the distinctive white and lighter polymer case rifle ammo. News like that always spreads quickly on the Internet and infantry worldwide pay attention.