Underhammer build nipple hole.

[Sinner]

I'm wondering about the tapped/drilled hole for a underhammer rifle build. Should the 1/4 x 32 threads go all the way into the barrel, or should there be a "shoulder" at the bottom of the threads?

[flintboomer]

The shoulder is on the nipple, but underhammers typically use a nipple with a deeper threaded portion because it goes straight into the barrel unlike a standard  sidelock which goes into a bolster or drum.

[Papa]

Flintboomer has got it right, the nipple should be fitted to the inside face of the bore. If you are drilling and threading the nipple hole, why not go to a standard 1/4X28? They are more widely available and can be gotten with several different thread lengths to accomodate a variety of barrel wall thicknesses.
Mark

[gunmaker]

TOW has longer thd. 1/4"-28 nipples for UH guns...

[Sinner]

Flintboomer has got it right, the nipple should be fitted to the inside face of the bore. If you are drilling and threading the nipple hole, why not go to a standard 1/4X28? They are more widely available and can be gotten with several different thread lengths to accomodate a variety of barrel wall thicknesses.
Mark

I was looking at 1/4x32, because that was the original H&A underhammer nipple size, (as I was told).  My understanding is that the fine threads are stronger that the coarse threads, due to more surface are in contact. Once again, as I was told (by a machinist). I've heard stories of some people having their nipple blown out... (just realized how that sounds), or the guns anyway. Just stories I've heard, but have no direct knowledge of. I would suspect that a cause could be worn threads.
Some people propose creating a "chamber" in a longer breech plug, with a smaller hole beneath the nipple threads, leading into the chamber. To me, that defeats one of the advantages of the UH, which is fire directly to the charge.
Just wanted to get some more input....
Thanks!

[Rev]

Flintboomer has got it right, the nipple should be fitted to the inside face of the bore. If you are drilling and threading the nipple hole, why not go to a standard 1/4X28? They are more widely available and can be gotten with several different thread lengths to accomodate a variety of barrel wall thicknesses.
Mark

I was looking at 1/4x32, because that was the original H&A underhammer nipple size, (as I was told).  My understanding is that the fine threads are stronger that the coarse threads, due to more surface are in contact. Once again, as I was told (by a machinist). I've heard stories of some people having their nipple blown out... (just realized how that sounds), or the guns anyway. Just stories I've heard, but have no direct knowledge of. I would suspect that a cause could be worn threads.
Some people propose creating a "chamber" in a longer breech plug, with a smaller hole beneath the nipple threads, leading into the chamber. To me, that defeats one of the advantages of the UH, which is fire directly to the charge.
Just wanted to get some more input....
Thanks!

About 12 years ago I was standing behind a lady shooter "spotting" for her. When she fired I felt something zip by my ear. Turns out it was the nipple from her rifle, so it can happen...

[flintboomer]

I have had a nipple blow out on a brass frame rifle with a heavy hunting load before, but if the threads are not worn out like they were on that one it should not happen. I had installed a .285 nipple due to wear and tear but did not know about using shotgun tube lube on the threads and back then I always removed the nipple as part of the cleaning process.

I posted a couple of years ago about finding a problem with a couple of my 1/4 x 28 nipples that were severely undersized (.235) and discarding them after I got home and measuring them, but they did not blow out even though the one in the rifle "jumped the threads" when I tightened it.
I tend to use fairly light loads for most of my shooting but that rifle has a Sharon barrel that likes 85 grains of FF and nothing less than 75 gr FF shoots well in it so I was NOT using light loads that day and it still did not blow, but I stopped shooting immediately after firing that load out.

[Papa]

I had a nipple blow out of a drum once but afterward felt that I had just not snugged it down and it worked loose over the course of a number of shots. It was an offhand rifle and I was shooting 50-60 grain charges. I have used UH's for offhand rifle, chunk guns and shotguns and with some real stout loads and never had a problem. I have a friend with a 1.5" bore cannon that he fires with a #11 cap and hasn't had any problems. If the nipple is fitted properly it will stay where you put it.
Mark