The OM 50 Nemesis is a bolt action sniper rifle made by Swiss manufacturer AMSD. It was created in early 21st century. It fires the .50 BMG bullet. It is a derivative of the french sniper rifle Hecate II made by the manufacturer PGM.
The concept, for what later became the "Nemesis" large caliber sniper rifle, was devised in 2001 by two former military, the retired US Marine Corps officer, James Owens and the Swiss Chris Movigliatti. First prototype was tested only 3 months after the design inception. In 2003, first production batch of rifles was made by AMSD, a Swiss company, highly specialized in the design of precision military light armament. The new weapon was officially christened as the OM 50 Nemesis (OM standing for names of the designers, 50 for caliber and Nemesis for the ancient Greek goddess of justice and vengeance).
The prime niche for this new weapon is precision anti-material shooting for military and police applications. The weapon can be configured as well for urban warfare as for long range target operations. A civilian version exists also for long range precision shooting. For this reason, the OM 50 Nemesis rifle features a fully modular design with three basic versions, known as Mk I, MK II and Mk III respectively. Each of these versions can be fitted with a variety of quick-change barrels, of different profiles and lengths, as well as with different add-ons (high efficiency muzzle brakes or detachable silencers / sound moderators). Barrel lengths vary from 381 mm / 15 inches for short range (urban) shooting against hardened targets and up to 838 mm / 33 inches for accurate long-range shooting. Barrel change can be accomplished in the field in less than 2 minutes, using a DIN screwdriver.