I got a new 54 cal GM slow twist dropin for my '80's T/C Hawken yesterday. Took it to the range, and had some 777 that I wanted to try that I've had a while. All I had was hang fires. I was using standard #11 caps and the nipple supplied on the barrel. I have since read that I probably should have expected that. Anyway, I noticed the nipple on the original barrel was shorter, and has a much bigger flash hole. I don't remember if it is a short T/C nipple or if I replaced it years ago. I decided to swap them as part of my quest for more reliable ignition, as switch to Pyrodex. The T/C nipple fits slightly looser in the GM than the GM nipple does, but it tightens up when fully seated. My question is: are these nipples supposed to be interchangeable. The GM nipple fits the T/C slightly tighter that it's original nipple does too, but it goes in an seats fully.