Pressure at Nipple

[RMAMYWAY]

Just picked up a clean T/C .54 Renegade caplock. Looks good, shot it about 15 times. Shoots good. As I was cleaning it with a wet patch I noticed water bubbling up around the nipple threads. Nipple is tight, and looks great, as I had checked it before I shot.  The flash channel hole under the nipple makes a right hand turn before it goes into the barrel. No signs of powder around the nipple from the barrel. I havent removed it yet, and I have a question. How much pressure is there at the nipple, and what would it take to blow it out. I am going to order a new breech anyway from the track.

[smokinbuck]

Jack,
If there is a problem with the nipple threads you can send it, the barrel, back to TC. They have a lie time warranty on their rifles wether you are the original owner or not.
Mark

[R. Nance]

Jack, ou may want to check the nipple to see if it is the correct one. There are several sizes out for diffrent mfg. of guns.

[Roger Fisher]

And might she be or have been cross threaded?   That's a no no!  I have seen them come out for that reason...

[William Worth]

If you turn the nipple just loose of being seated, is it wobbly in the threads?

Maybe it needs to be rethreaded to a larger size.

[RMAMYWAY]

Thanks for all your replies. I plan on replacing the breech. I unscrewed the nipple and it looks like some of the bottom threads of the breech are damaged. It was held in place with about 3/4 of the nipple threads. Obviously it was holding for all my shooting, which makes me wonder how much actual pressure is there on the nipple?

[Daryl]

If the main charge manifests 15,000 pounds per square inches, how much area is the bottom of the nipple. I think you can divide the area into a square inch, then multiply by 15,000 and that's the PSI on the nipple.

[Dave Faletti]

Pressure at the nipple is the same as at the breech.  The force is what the question appears  to be and the number Daryl is coming up with.  Area for a quarter inch nipple is about 0.05 square inch.  15,000 X 0.05 = 735 lbs.  Sorry to be picky on terminology.

[Dave Faletti]

I used the major thread diameter to keep it simple.   I believe 15Kpsi is high but pick whatever number might reflect your load.   The diameter of the passage from the nipple to the bore won't change things.  The hole thru the nipple is so much smaller than the passage the nipple will see essentially all the pressure.

[William Worth]

I do wonder though if flash channel geometry would reduce pressures.  In one modern gun there is a system used "delayed impingement gas system" or some such in which the barrel gas is routed around a turn or two to delay and reduce gas pressure to the piston that drives the bolt.