The XM109, originally known as the Objective Sniper Weapon (OSW) and now called the Anti-Materiel Payload Rifle (AMPR), is a semi-automatic grenade launcher, designed primarily for engagement of
light armored vehicles and similar targets. The design uses the lower receiver from an
M82/M107, but with a new upper receiver chambered in 25mm. The upper receiver of the M82 rifles can be replaced with an XM109 upper receiver to form a fully functional XM109 rifle. The
25 × 59 mm round that is used in the XM109 is the same one originally developed for the cancelled
XM307, product of the Objective (later Advanced) Crew Served Weapon program (OCSW / ACSW). As with the XM307, the XM109 can be reconfigured back to
.50 BMG, in the XM109's case this is done by swapping the 25mm upper receiver for a standard M82 / M107 upper. The XM109 offers greater range and a shorter overall length than the previous M82/M107 systems, as well as potentially greater power in the 25 × 59 mm cartridge over even the
Mk 211 .50 BMG cartridge (AKA "Raufoss round"). However, the small amount of propellant and heavy projectile resulted in unacceptably high recoil due to limiting the effects of the weapon's
muzzle brake, with a recoil force of over 60 foot-pounds compared to 36 for the M107. As of 2004, one of the project goals was to reduce the weapon's recoil. ==Features==