M Series

The M series of weapons was discontinued in favor of the R series in the early 21st century according to the description of the R91 Assault Rifle in a Citadel terminal in Fallout 3, although this contradicts the information in the Museum of Technology about the M199 still being the official U.S. Army weapon (stated in present tense). It is a possibility that the museum's exhibit was in place before the military made the decision.

Known models

 * M1 Garand
 * Browning M2
 * M-14
 * M16A1
 * M60
 * M72 Gauss rifle
 * M79 grenade launcher
 * M199 assault rifle
 * M249 SAW
 * Calico M950