Back from the range, up to 500 rounds now. Prone unsupported at 100 I achieved a 10 round group 1.25" wide by 3.5" tall (bad breath control) with M855. I had issues with the Elander magazines I brought out but only when resting the rifle on the magazine (failure to fully seat, the mag rubs the bcg) otherwise there were no issues. Pmags are fine to rest on but those are the only two I've tried so far. The metal shavings I mentioned earlier are brass 100%, the extractor must just be sharp or something as all the brass had a tiny sliver removed. I detail cleaned the BCG and upper to look for flaws and all I've found is that the cotter pin has wear on it from the firing pin- the firing pin is fine and none of the brass bits got anywhere concerning, most ended up on top of the lower on either side of the magwell. Nothing unusual anywhere else so far. I am going to replace the firing pin spring as well but if it continues to perform as it has on the range I will be very pleased with its performance. I'm done making posts til I've finished my thousand rounds. I hope this gives you an idea of what you can expect.
Awesome to hear. And thanks for the updates. Looking forward to getting mine back whenever they are done the cosmetic work, then I can check out the internals and get to having some fun.