Patent attributes
A system for firing reduced energy cartridges from a modern sporting rifle utilizes a bolt assembly weighing less than a conventional bolt assembly for such rifles and utilizes blow back for cycling the bolt assembly rather than gas operation. A bolt insert in a polymer bolt carrier of the bolt assembly has a projection that fits within a recess on the rear face of reduced energy cartridges. The reduced energy cartridges having a polymer casing, a rimfire power load for propellant, the power load recessed from the rear face of the casing. Tuning the bolt may comprise adjusting the weight of the bolt or the sliding resistance of the bolt assembly in the upper receiver. The bolt may be formed by metal injection molding with a polymer bolt carrier attached thereto.
