US Patent 7478495 Mechanical buffer for shouldered weapon

A weapon includes a receiver having a bolt carrier assembly therein; a buttstock disposed behind the receiver, the buttstock having a tubular opening adjacent an end of the bolt carrier assembly; a larger diameter spring disposed in the tubular opening; a smaller diameter spring disposed in the larger diameter spring; a rod disposed in the rear end of the smaller diameter spring; a bumper attached to the rod; and a cap disposed in the front end of the spring, the cap having a head wherein a front side of the head engages the end of the bolt carrier assembly and a front end of the larger diameter spring bears against a rear side of the head.