Reduced energy MSR system

A converted modern sporting rifle in combination with reduced energy ammunition, the modern sporting rifle converted from gas operation to blowback operation, the modern sporting rifle before conversion comprising a conventional bolt assembly weighing greater than 10 ounces, a first recoil spring for the bolt assembly, and a firing chamber sized for one of a .223 Remington, a 5.56×45 mm NATO cartridge, 7.62×51 mm NATO, and a 7.62×38 mm cartridge, the modern sporting rifle after conversion comprising:

• a replacement bolt assembly comprising a bolt carrier with a bolt insert fixed within the bolt carrier, the bolt insert comprising forward lugs and a forward face sized for a cartridge of the reduced energy ammunition, and a metal firing pin extending through the bolt insert, axially movable within the bolt insert, and offset from the center of the bolt insert;
• the reduced energy ammunition comprising a cartridge with an exterior casing sized to conform with one of .223 Remington, a 5.56×45 mm NATO cartridge, 7.62×51 mm NATO, and a 7.62×38 mm cartridge, the cartridge comprising a case comprising a reduced energy power load with propellant fixed in the case, a projectile, the projectile weight and the ropellant selected to provide a muzzle energy of the projectile leaving the rifle in the range of about 50 ft-lbf to 400 ft-lbf, and
• wherein the mass of the replacement bolt assembly is configured such that the replacement bolt assembly is configured to move in a rearward direction and compress the first recoil spring by a distance upon firing of the cartridge, the distance being large enough so that the casing of the cartridge is ejected and a second cartridge of the reduced energy ammunition is fed into the firing chamber by blowback operation of the rifle.

A converted modern sporting rifle in combination with reduced energy ammunition, the modern sporting rifle converted from gas operation to blowback operation, the modern sporting rifle before conversion comprising a conventional steel bolt assembly weighing greater than 10 ounces, and a firing chamber sized for one of a .223 Remington, a 5.56×45 mm NATO, 7.62×51 mm NATO, and a 7.62×38 mm cartridge, the modern sporting rifle after conversion comprising:

• a replacement bolt assembly comprising a polymer bolt carrier with a metal bolt insert fixed to the polymer bolt carrier, the bolt insert comprising forward lugs, a raised portion, a forward face on the raised portion, and radiused relief shoulders at the base of the raised portion, the forward face sized to be inserted beyond a rear face of the cartridge;
• the reduced energy ammunition comprising at least one cartridge with an exterior casing sized to conform with one of a .223 Remington, a 5.56×45 mm NATO 7.62×51 mm NATO, and a 7.62×38 mm cartridge, the at least one cartridge comprising a case comprising a rear face and formed from a polymer, a power load with propellant comprising an anvil recessed from the rear face of the case, the case defining pathway to a projectile, the projectile weight and the propellant selected to provide a muzzle energy of the projectile leaving the rifle of less than about 840 ft-lbf, and
• the mass of the replacement bolt assembly is configured to, upon firing of the at least one cartridge, eject the casing from the firing chamber and feed a second cartridge of the reduced energy ammunition into the firing chamber by blowback operation of the rifle.