I'm working on the metal parts on the shotgun I posted that I'm rebuilding..Everything in good shape other than the nipples..Tops are terrible deformed..Thread is almost dead on 1/4-28,but a 1/4 -28 bolt drops right in,hole a little big..Now,I can fix the nipples and put them back in,but is there a common weird thread I can just buy to replace them? A kit with a tap?