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Caseless ammo could cut 25 lbs. from gear

May. 21, 2012 - 08:20AM   |   Last Updated: May. 21, 2012 - 08:20AM  |  
Caseless ammunition and The Lightweight Small Arms Technologies machine gun to fire it are being developed in an effort to decrease the weight Marines and soldiers carry into battle.
Caseless ammunition and The Lightweight Small Arms Technologies machine gun to fire it are being developed in an effort to decrease the weight Marines and soldiers carry into battle. (Courtesy of Textron Systems)
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Dropping weight

The Marine Corps and Army are developing new ammunition that, when partnered with compatible weapons, could cut some serious weight from the gear troops carry in combat. A look at the numbers:
M249: 51.3 pounds when fully loaded with 1,000 rounds of linked ammo 17.5 pounds for the weapon, 33.8 pounds for the ammo.
Marine upgrade: 26.9 pounds 9.9 pounds for weapon, 17 pounds for ammo.
Army upgrade: 30.6 pounds 9.4 pounds for weapon, 21.2 pounds for ammo.

The Marine Corps and Army are developing new caseless and case-telescoped ammunition that, when partnered with a new light machine gun also in development, could significantly cut the burden on troops in combat. And perhaps more significant than that, in the coming years this revolutionary ammo could drive production of the Corps' next service rifle.

Caseless ammunition, which is free of the heavy brass casings found on traditional cartridges, will allow Marines to carry more rounds or simply shed weight up to 25 pounds for the typical M249 Squad Automatic Weapon gunner, said George Solhan, the Office of Naval Research's deputy chief researcher for expeditionary maneuver warfare. Some of the ammo and weapon systems now in development could be ready for action in just a year or two, according to researchers.

But to make that happen requires a commitment from military and civilian leadership to speed the ammo's development and an entirely new line of compatible infantry weapons, Solhan said. The associated cost and effort has caused many to give pause. And while Solhan acknowledges that pushback, he dismisses it as shortsighted given the potential payoff for infantrymen.

"For the cost of a couple of current-generation jet fighters," he said, "you could do that for the entire Army and Marine Corps."

A new light machine gun could be fielded within two years if military leaders and lawmakers on Capitol Hill put their unequivocal support behind the project, he predicted. There are nearly a dozen working prototypes of what is known as the Lightweight Small Arms Technologies machine gun. To the user, it looks and feels like a conventional machine gun, but at less than 10 pounds, it is nearly half the weight of an M249 SAW. And there is additional weight savings when comparing the new ammo to standard 5.56mm rounds.

Here, the Marine Corps and Army are working on separate scales. The Army is further along in developing what are known as case-telescoped 5.56mm rounds, which use a polymer cylinder that entirely encases the bullet and propellant, and pose fewer technical challenges than caseless ammo. A thousand rounds weigh about 21 pounds, versus nearly 34 pounds for the SAW. Field tests already are underway.

What the Corps wants

The Marine Corps' approach calling for caseless rather than case telescoped is more extreme and will take several years to refine, according to Paul Shipley, program manager for Textron Systems' Lightweight Small Arms Technologies project. A thousand rounds weigh just 17 pounds half the load of standard 5.56mm rounds used by SAW gunners now.

The Office of Naval Research is working with industry to refine a cartridge that uses propellant mixed with binding agents to form a durable solid cylinder. The bullet is contained inside the cylinder.

The entire round is fed into the chamber, and upon ignition the primers and propellant case are consumed, leaving nothing to be ejected. The ballistic qualities of the bullet in flight are nearly identical to current cartridges, and the new rounds are in fact safer because they are less likely to explode when exposed to fire, developers say. That, paired with an innovative mechanism known as a "rotating chamber" pioneered by Heckler & Koch in the 1980s, makes for a highly reliable machine gun that should help eliminate failures, according to designers.

The rotating chamber moves in line with a feed tray above the barrel. A belt-fed round is rammed in and the chamber swings down, in line with the barrel, before being fired. The chamber then oscillates in front of the belt to accept another round. If a chambered round fails to fire, the following round will simply push it out the front of the chamber, ejecting it. The gun continues to fire without missing a beat, Shipley said.

Marine officials say they are working diligently to develop the technology, which will be seen first in large-caliber crew-served or mounted weapons like the .50-caliber machine gun.

"We believe near-term transition of caseless or case-telescoped ammunition to purpose-built remote weapons in larger calibers is the most effective and efficient application of this technology based on technical maturity, existing capability gaps, and the constrained fiscal environment," said Col. Sean Gibson, a spokesman for Marine Corps Combat Development Command in Quantico, Va. "Our mid-term objective is to transition LSAT technology to small arms in our next service rifle and other systems."

It's unclear exactly how far the Corps is from meeting those short- and mid-term objectives, but Shipley said caseless ammunition is at "Technology Readiness Level 5," meaning not yet ready for field trials and still being perfected in labs. But the prototype light machine gun that now fires case telescoped ammo could be retrofitted with just a few changes.

The Marine Corps has begun moving toward a lighter alternative to the SAW, replacing it in some settings with the M27 Infantry Automatic Rifle. Critics said it was a dangerous downgrade in firepower. The SAW is belt-fed, meaning it can put hundreds of rounds downrange uninterrupted. The IAR, on the other hand, uses 30-round magazines, meaning even though it can fire in full auto mode, it has more difficulty putting down a constant stream of suppressive fire.

Army out in front

The Army will likely get out ahead of the Marine Corps with next-generation ammunition and weapons, simply because the development of case-telescoped ammunition is further along. While it does not offer as much weight or space savings, it is a vast improvement over conventional brass-cased ammunition. Already at Technology Readiness Level 7, the ammo is working and there are nearly a dozen prototype weapons, Solhan said.

One of those, produced by Textron Systems, was tested by the Army with 50,000 rounds over three weeks in September at Fort Benning, Ga., receiving positive marks from Army officials who coordinated the trials, according to Shipley.

Case-telescoped rounds offer fewer developmental challenges than caseless rounds. To launch a projectile forward, the pressure generated by propellant has to be directed down the barrel, behind a bullet. The brass casings on cartridges used in conventional firearms are malleable, meaning they expand slightly under pressure in the chamber and create a seal. The polymer case serves the same function.

But with caseless ammunition, in which the entire structure of the round is propellant, there is nothing to expand and create a seal. That means engineers have to devise a separate mechanism to create a seal.

The search for caseless ammunition began in the 1980s under the Army's Advanced Combat Rifle program. It was abandoned, but in 2004 Army leaders renewed efforts to cut weight. They identified ammunition, along with personal protective equipment, food, water and batteries, as the heaviest things soldiers carry.

The time to take the next step is now, Solhan said.

"Our current infantry rifle is 50 years old, and it is a very good rifle. It has gone through a number of improvements, but it is probably not going to get any better than it is because it is very mature technology," he said. "And so today, we can save a significant amount of weight, maintaining the exact same ballistic performance, by using caseless ammunition. If we were really serious about saving weight, what is bad about saving 25 pounds of weight for one guy?"

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