07-04-2018, 03:52 AM
DPMS pattern large frames (which is what the majority of do-it-yourselfers do) use standard AR 15 tubes with heavier buffers and springs, but there are a lot of proprietary large frames out there including RRA and POF (where I ultimately gave up on trying to get a rifle stock to work on my P308). I'm pretty sure the SR 7.62 is proprietary, but I was under the impression that Ruger contract out most of their AR assembly. If it was a large frame lower, it wouldn't fit into an AR 15 upper.
Let's go Brandon!