Just a follow-up on this ... I actually ordered a Hot Shot nipple to see if this would make a difference. The results were somewhat unexpected and unpleasant.
The nipple looked great and of course installed just fine. I put a (CCI Magnum) cap on it with my capper and seated it firmly with my thumb, just to be sure. It was on firmly. Snapped the cap and ...
Nothing. The hammer falls with no effect. Okay, try again ... Nothing. At this point I look carefully and see that although it looked like the cap was correctly seated (from all I could see), it was now apparent that it hadn't seated quite all the way, and the hammer blows had slightly mushroomed the top of the cap as they'd driven it even more tigntly onto the nipple. Okay, so try to pull it off ... No way.
I carefully made several attempts at getting it off, but without success. It's ON there! So I carefully remove it from the rifle, put the (thoroughly cleaned) TOW stainless nipple back in, and everything works perfectly. No failures to fire since. So now I have a Hot Shot nipple with an unfired cap FIRMLY stuck on it.
When I get around to it, I'll get that cap off one way or another, without harming the nipple. It could be just one of those odd differences in fabrication that happens now and then where the nipple diameter or cone angle didn't come out quite right. I'm sure I can fix that, but I'm curious if anyone else has encountered this problem with Hot Shot nipples.