I know there are black gun forums out there, and this question might be better suited for them. I was thinking about building an AR 10 and was wanting to put a compteition barrel on the gun. Looking online, barrel manufacturers specify whether it fits an Armalite, or a DPMS. it seems the barrels are not interchangable. I know that the AR10 is not nearly as stardardized as the AR15 and that you cannot just buy parts anywhere and from whoever and expect them to fit, but what is the actual difference that makes these barrels spcific to the make?