Precision-machined, stainless bolt-and-carrier group features JP's enhanced bolt made of high-grade 9310 steel for a significantly longer life expectancy than standard mil-spec bolts. Set is available with choice of JPBC-2A Low Mass carriers that reduce felt recoil and increase bolt speeds slightly for enhanced rapid fire handling, or the standard JPBC-2A Full Mass carriers that replicates the normal carrier weight and is preferred for duty rifles or any time absolute reliability is required. Standard weight carrier features a 100% increase in bearing surface for smoother cycling and reduced wear on the inside of the receiver. Both the JPBC-2A carriers feature JP's super-hard Mfg: J P Enterprises