Solid lubricant smooths the way for reduced weapon maintenance

Covered with a durable solid lubricant, the bolt and bolt carrier assembly are inserted into a weapon’s upper receiver(Credit: US Army/Erin Usawicz)

One the most tedious yet vital tasks of the foot soldier is personal weapon cleaning and maintenance. Under field conditions, it has to be done daily and failure to do so can literally mean the difference between life and death. To reduce this task and make the weapon more durable and reliable, the US Army Research, Development, and Engineering Center (ARDEC) at Picatinny Arsenal, New Jersey is developing a Durable Solid Lubricant (DSL) that replaces the more conventional wet lubricants.

Weapon cleaning has been the soldier's lot ever since the invention of gunpowder. Despite centuries of advancement from simple fire tubes to advanced automatic assault rifles, the routine of stripping and cleaning has remained as predictable and necessary as ever.

This is because firearms are made of a precisely engineered set of slides and linkages to load and fire, and the barrel to hold the ammunition and send the bullet on its way. Lubricants are needed to make sure the moving parts operate quickly and smoothly, but the inside of a rifle is very hostile to mechanics.

As the cartridge fires, the barrel becomes a space filled with hot, corrosive gases, which leaves behind a stubborn carbon residue that, if not removed regularly, will increase wear and cause the firing mechanism to jam. Worse, dirt and sand can find their way in and cause even more trouble.

The problem is that most weapons use CLP (cleaner, lubricant, and preservative), which is a wet lubricant. Cleaning a rifle not only removes the dirt and residue, but the CLP as well, which has to be continuously replaced.

Since 2001, this problem has become more acute for the US Army and Allied forces with the outbreak of the Global War on Terrorism. Weapons designed for wars in Europe or the tropics ended up being used in the sand and grit of the Middle East, where many rifles and other weapons saw a jump in wear and jamming of some types occurred with alarming frequency if cleaning procedures were neglected.

As part of the US Joint Service Small Arms Program, engineers at ARDEC were called in to find a lubrication solution that didn't rely on CLPs. Using as a baseline small and medium caliber weapons, such as the M4A1 Carbine and the M240 machine gun, they came up with a solid lubricant that allowed the weapon to continue to function with less maintenance.

Instead of being applied to the weapon directly, the DSL is coated on the components during manufacturing. According to ARDEC, the DSL has a lower friction coefficient to allow the mechanism to slide more freely, better wear resistance, and improved corrosion protection.

"With typical wet lubricants, Soldiers need to reapply in order for the weapon system to function properly. Soldiers also have to regularly clean off carbon residue that builds up from firing and it can be tough to clean," says experimental engineer Adam Foltz."Our DSL has a high wear resistance and a low friction coefficient, so it's easy to clean off anything that builds up. You can use a steel brush to knock off any residue, and you don't even have to worry about reapplying anything."

ARDEC says that using DSLs also eliminates the need for phosphate coating and oils, so it's more environmentally friendly.

The precise nature of the new DSL hasn't been released, but most solid lubricants are made from a variety of materials, such as ceramics, soft metals, and nanotubes. ARDEC says that the development process started out with 27 candidate coating combinations, which were reduced to six by coating metal balls with the candidate material, then bringing them into rotating, sliding contact at a specified load against three pads. These pads were also coated with the candidate coatings and the tests carried out under various environmental conditions.

The six winners were then subjected to a slide-rail simulator, which reproduces the typical geometry, motion, and contact stresses in a gun. The best four candidates ended up in live-fire exercises of up to 15,000 rounds per weapon while subjected to different temperatures, sand, dust, salt, and fog.

The result was a DSL that demonstrated five percent wear on the bolt carrier and bolt, while a control CLP showed 75 percent wear on the bolt carrier sliding surfaces and 90 percent on the bolt.

ARDEC says that the DSL is currently undergoing larger scale testing in hopes of moving it into the field in 2017. How well it works then will show if it lives up to its promise under real world conditions. In the meantime, the agency says that the technology could find applications in other armament systems, manufacturing machinery, and advanced oil-free turbomachinery.

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