The USAMU Custom Firearms Shop produces top-quality, match-grade rifles, pistols and shotguns, as well as much of the ammunition for the Army Marksmanship Unit. The Firearms Shop has a long history of research and development, including developing and testing the M-21 and M-24 Sniper Systems and Special Reaction Teams Rifles, and testing and maintaining the Barrett 50-caliber Sniper Rifle and development or modification to special operations forces weapons. The most recent achievement by the shop is the "accurization" of the M-16A2 Rifle and the M-9 Pistol, in which the gunsmiths, machinists and ammunition technicians transformed the reliable combat weapons into match-winning equipment, and the Mk-12 currently being used in Operation Enduring Freedom and Operation Iraqi Freedom.

The Soldiers of the USAMU Ammunitions Loading Section produce world-class match ammunition for the shooters of the U.S. Army Marksmanship Unit. They are responsible for the thousands of rounds produced each day — each measured and adjusted to within 500ths of a grain. They produce ammunition for rifles and pistols and test each cartridge case, propellant, primer and bullet.