The new Smith and Wesson M&P15R is a rifle chambered in 5.45×39.  S&W developed this new AR variant due to the rising costs of .223/5.56 NATO ammunition.  The 5.45×39 cartridge was developed for the AK-74 rifle in the early 1970s.  Few guns in made the United States are chambered for it, and consequently, surplus ammo is comparatively cheap.  The 5.45×39 is not interchangeable with the 5.56×45 NATO (or .223 Remington) cartridge which is the standard cartridge AR-15 platform rifles.
The M&P15R features a chrome-lined 16″ barrel with a 1:8″ twist, M4 style post front sight, and a six-position collapsible stock. The rifle comes with one 30-round magazine.
A “mil-spec” upper is also available for people who already own an AR, but would like to shoot 5.45×39. The upper comes with a 30-round magazine and a bolt carrier assembly and should drop right onto any mil-spec AR lower.
The M&P15R has a suggested retail price of $1146.00 and the upper alone has an MSRP of $751.00. Â Street prices should be significantly less.