Milsurp is short for "Military Surplus". Thanks to various reasons, including the UN's insistence on the destruction of usable firearms which are being phased out by countries and a restrictive mesh of importation restrictions, most serviceable milsurp firearms are eligible for C&R status by the time they reach the American market.
Military surplus weapons exist in a wide variety of calibers and configurations. The most available ones on the market presently are: