Although composite materials often carry enormous potential for weight reduction, Army scientists are finding that redesign and the combined use of various metal alloys are equally important keys to reliable and easily portable weapons.
The new arms being designed at the Army's Soldier Systems Center in Natick, Mass., use blends of conventional metals, newly developed materials and novel approaches to firearm configurations. Testing that once took years to accomplish now takes months, with the help of computer modeling and advanced testing chambers.
"We're not stubby pencils and blueprints any more," said Lt. Col. Matthew T. Clarke, program manager for individual weapons at Natick.
Replacing parts with new materials is not new. Butt stocks for the M-16 and M-4 were replaced with composite carbon after it was determined that soldiers were cracking the rifle's stocks when they dropped to the ground after a dash. But enhancing performance while keeping the same dimensions as old systems is a hard nut to crack. Researchers say the chance of success is increased dramatically when they design from scratch instead of retrofitting existing platforms with lightweight pieces.
"Brass casings are great. They've been around forever for a reason ... But is there anything other than brass? We're looking at that right now," said Richard Audette, deputy project manager of soldier weapons. "All the solutions so far have been thicker."
One project on the front burner is the XM25 25 mm airburst weapon system. The weapon features a single piece of carbon-fiber composite material making up the weapon's stock and frame, with a titanium barrel and a scattering of internal steel components.
"We think we've gotten the mixes correct," Clarke said. "This represents a significant leap ahead for lethality,"
The XM25 uses a variety of specially crafted munitions, including non-lethal and high-explosive variants, featuring steel warheads and aluminum casings. A shooter lases a target with a range finder as the weapon's internal ballistics processor speaks to the smart round, informing it of environmental conditions. If the shooter wanted the round to explode after entering a room through a window, for example, distance can be manually added to the fuse's timer. The system weighs less than 12 pounds.
The XM25 program enters the demonstration and development phase next summer, Clarke said.
Another new weapon using a radical design to complement composite materials is the XM312, a .50 caliber machine gun with a sliding barrel design that decreases the recoil energies. The barrel and other subsystems are pushed forward by a spring when the weapon is fired, the moving parts reducing recoil significantly. When fired, the barrel appears to move in and out like a sewing machine needle. The system is made from a carefully selected mix of stamped aluminum, composite carbon fibers and steel for internal mechanisms.
The system weighs 29 pounds, plus a 13-pound carbon composite ground mount. The XM312 can be converted to a 25 mm weapon by using a five-part kit. That system, XM307, can fire the same selection of rounds as the XM25 airburst system.
"We design to get as much commonality as we can," Clarke noted. Sometimes composites bring other advantages, such as a lack of corrosion, overall strength and resistance to weather. …