After several outings at the range, I took my Pietta apart and cleaned it. I decided to take the nipples out as well. Maybe a mistake as I cannot get one of the nipples to start back in. I got 5 of them in with no problem but the sixth will not start. I have the proper nipple wrench. When I start it, I can feel it catch and then at about 1/2 to 3/4 of a turn I can feel it come out. I tried for an hour and finally gave up (came close to throwing it across the shop!!!). Must be buggered up but not sure how it got that way. I guess I will need to start a tap in it but do not know the correct size and doing that makes me a bit nervous. When I got the gun new from Cabela's I shot it quite a bit. Then I replaced the nipples with new ones from Track of the Wolf and all was well until this happened. Any suggestions or do I need a gunsmith? Thanks.