Had problems with remingtons years ago not firing so quit using them and use only CCIs or Vol??? something cant spell it. May be time to change out the nipple. Had one several years ago that had a lot of no fires and found the end was flattened out a little. Also on a side lock the hammer hits the nipple at just an ever so slight angle, unlike an inline where the nipple is struck with a straight more seven strike, this could cause the nipple end to flare/ flatten. Also most don't think of this but thru out years of use taking caps on and off can wear the nipple. Even very small amounts of basically metal rubbing on metal will cause some wear. With caps and nipples it doesn't take a lot. Also size varies just a tad from manufacturer to manufacturer. Example I have a Traditions 1858 Remington 44 revolver that shoots #10s and some are a pain to get on/off and some will simply just fall off. Also have a Traditions trapper 50 cal pistol that's supposed to take #11, but they are loose and #10 are a little to tight. I would change the nipple as they are cheap and if that doesn't work it won't hurt to have a spare. If you change nipples and failure to fire stops but the cap is still loose PM me and I will tell you how to fix that.