This short post of from the Special Forces Association.
The Barrett XM109 is a prototype anti-materiel precision rifle, chambered for 25 × 59 mm grenade rounds and developed by Barrett Firearms Manufacturing.
It was designed in accordance with a requirement set out in 1994 and is capable of defeating light armor and equipment out to 2 km (1.2 mi).Prototypes of the XM109 have existed since the late 1990s and studies of the weapon’s effectiveness were released in 2002; 10 prototypes were known to exist in 2004, and the XM109 and Barrett XM500 were folded into a broader Anti-Material Rifle Congressional Program in 2006. The current status of the XM109 is not particularly clear, with no news of either cancellation or potential adoption.
The XM109, originally known as the Objective Sniper Weapon (OSW) and now called the Anti-Materiel Payload Rifle (AMPR), is a semi-automatic anti-materiel rifle, 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.