AR10 Lower

 That’s a loaded question because none of the Armalite AR-10 models were adopted by the DoD/military, so there would not be a mil-spec for those firearms. However in the case of our SR25 / AR10 80 lower, we have designed it patterned after the original Armalite AR-10 A-model. That profile is common among the AR-10 profile rifles and lowers currently available such as the SR25 rifle for example.For our DPMS Gen-1 LR-308 80 lower receiver, we purchased a DPMS upper and lower receiver set, and then reverse engineered them. Our lowers fit their upper perfectly, and our upper fits their lower. Even though there is no actual mil-spec for the 308 AR-10 models, we machine our billet aluminum lowers to tolerances tighter than typical shop tolerances of +/-0.005″., And since we machine the entire lower, faces and all, we hold those much tighter machining tolerances. ar10 lower