I wonder if the bolts marked HP MPI fail as much? I do know guys that take RRA, Bushmaster, commercial guns to AR classes experience bolt failure more often. Heat em up beyond coyote hunting and plinking and things change! lolall parts fail at some time or another regardless of price. if the failure was due to something other than usage, more info about the firearm would be needed (maintenance, ammo, use of and more). make sure the barrel extension is clean and no excessive wear on it, check the cam pin channel on the receiver and chargehandle. if the gas rings or the carrier caused the bolt to fail, it could've caused this with excessive pressure when the pressure was supposed to be less during the cycle.