I have built a few lately. You need to do a little prep work. I have drill bits the correct size for all the drilled holes in the lower. Clean out all the holes "by hand" before assembly. This only takes a couple minutes, and saves lots of head aches. Upper and Lower lock up in my experience is a lot better than the uppers and lowers sold by others in years past. Most AR's that I put together over 15 years ago needed an Accu-Wedge to improve the sloppy fit. The last Five that I have put together Anderson Lower with Anderson, Aero, and Stoner uppers, all went together like a matched set. Quality Control seems to be a lot better now days.
Bob R
