guys, i need a little help. i've got a knight bighorn that i bought new back in 2011. decided to finally get it out and shoot it. the first time out (friday) i got 6 shots and the nipple warped and had hairline cracks. could not fit a cap on it after that. thought maybe i dry fired it and caused it. went and bought two new nipples and just got back from the range. the new nipple did the same thing?? what could be causing this? thanks in advance. my trouble sighting in will be another topic!!