I recently purchased a pre-ban Sendra lower from a member off the EE, and ordered a new BM M4A3 upper to mate to it.

I got the upper, and tried to fit it to the lower. I had to press them together quite firmly, and could only get the take-down pin in partially, not fully. Next I tossed the accu-wedge out, lubed the take-down and pivot, still could only get the tip and a fraction of it through the hole in the upper, but not out the other side. The pivot-pin mounts easily.

But being sure the two receivers fit now, being that I could get the pin started, I then just carefully tapped it home and through using a mallet and padding. Of course now I know I'll need the mallet and a punch to get them apart again.

My question is this: Am I being careless and stupid? Am I possibly forcing the issue too much? Maybe I need to have it fitted perhaps? It's nice and tight once in there, no play whatsoever, feels great! But I fear I'm placing undue stress upon the pin. Is this normal, does it just need to 'wear-in'?

Too tight is a lot better than loose. It will wear in.