Bolt Stop Problem on New Built Lower

Last night I got my newly built lower to the range. I’ve had the RRA lower and RRA parts for a year and just got around to assembling it. Without a parts list to ID the parts, it took just over an hour – really easy.

Everything worked except the bolt stop on the last round. The new receiver doesn’t catch the bolt face, but catches just behind the locking lugs. If I pull back on the handle it will lock, but on the last round it catches just behind the locking lugs.

I swapped out the buffer and spring with another lower that works, thinking that the spring might be too strong, but it still happened. I tried the new buffer and spring in my old lower and everything worked properly.

I tried both USGI 20rd magazines that I had with me, but it still happened. I tried both magazines in my old lower and everything worked properly.

Then I tried the “Bob SLED” (dedicated single shot magazine) that I had with me, the bolt stop worked properly.

My thinking now is that the problem is a combination of a little-bit weak magazine springs (they work in my other lower) with a new bolt stop that might not move as freely as the one in my other lower. Does this make sense? Any other theories?

If I remove the bolt stop and LIGHTLY stone the surfaces where it contacts the lower should that solve the problem?

I won’t be able to get back to the range for a few weeks, so I am I interested in trying a few things to solve the problem.

Thanks,
Jack

I,ve had a bolt stop that was not spec on the contour where it contacts the lower,,had to take some off with my dremal tool,,works good now--it was not making enough movement