Percussion pistol build question

[Eddie2002]

I'm building a .50 caliber smooth bore percussion pistol and have a question about the nipple drum. Should it be supported on the bottom by the lock plate? I'm asking because all of the factory fire arms I've seen have a small gap between the bottom of the nipple drum and top of the lock plate.
Thanks

 

[Flintandsteel]

Yes! Definitely! That will support the drum, and keep it from shearing off due to continuous striking of the nipple.

 

[bubba.50]

Ideally it should be supported. But not to the point of binding because too much upward pressure would be as bad as too much hammering from the top during firing. It’s just not practical to have tolerences that tight in mass production guns.

 

[hawkeye2]

Too much pressure and you will find the point of impact shifting as the barrel warms up.

 

[Dale Lilly]

Lyman recommends the small gap. [page36, illustration, in section 'instructions for Lyman assembly kits' in the Lyman User's Guide for Black Powder...' It is explained very well in an earlier post … but I don't remember where. Polecat

 

[Eddie2002]

Thanks, I'm just starting to inlet the lock plate and will set it up with some solid support for the nipple barrel. I've made a few rock locks but this is my first "stuff laying around the shop" parts build for a cap lock.

 

[Zonie]

Lyman recommends the small gap. [page36, illustration, in section 'instructions for Lyman assembly kits' in the Lyman User's Guide for Black Powder...' It is explained very well in an earlier post … but I don't remember where. Polecat

I think Lyman's instructions are for a gun with a snail type breech. Not for a barrel mounted drum which screws into the wall of the barrel.

With a snail type breech, the entire breech plug which is firmly screwed into the rear of the barrel, can take the blows of the hammer falling on the nipple without a problem.
With a side mounted drum that is screwed into the barrel the only thing that takes the impact of the falling hammer is the relatively small threads on the drum.
These threads are often as small as a 5/16-24 thread and to make matters worse from a stress standpoint, they have 1/8" hole going thru the center.
That is why it is imperative that the side drum is solidly supported by the lock plate, when the barrel is installed in the stock.
I do agree with the others that the fit of the drum with the lock plate should not keep the barrel from seating fully into the barrel channel so, this does take some careful hand fitting to get it right.

 

[Dale Lilly]

Zonie is absolutely right. I did not pay enough attention to the drum vs snail bit. I am wrong … pay attention Dale.

 

[Eddie2002]

Great , thanks for all the replies. I've lined the drum up to rest on the side plate and will fine tune it once the lock plate is fully inletted. Doing all the inletting with hand chisels so it's going to take a few weeks getting it right.

Proofed the barrel with the drum installed over the weekend with 70 grains of 3F and two patched round balls. Wired it to a 2x6 and buried it in a slit trench covered with a piece of diamond plate weighted down with fire wood, touched it off with cannon fuse with no damage and a lot of smoke.