Interchangeable touch hole/ drum for thin barrel.

[smallpatch]

Working on a little skinny ¾” barrel that client would like to make convertible.  Because of the thin walls, I’d like to use ¼”-32 threads for the touch hole, but don’t see a drum with those threads.

Any  input or ideas?  I’m leaning toward no!

[D. Taylor Sapergia]

I think you've found the correct answer.  That is a disaster waiting for a fool to try it.  I wouldn't touch that one with the proverbial pole.  Either it's a percussion rifle or a flint rifle, and I question too the percussion drum.  Just not enough support.   You don't memtion what calibre Dane...

[okawbow]

Would be easy to make a drum if you have a 1/4”x32 tap. I’ve made several. I think I’ve seen the dies on amazon.

[smylee grouch]

There are rifles out there with that setup and some say its OK and or safe but I always felt unsure about it. I did make a perc./flint conversion but it had an extra barrel/lock.   A late English L&R with two DeHass interchangeable barrels, both with hook style breechs.

[shifty]

Working on a little skinny ¾” barrel that client would like to make convertible.  Because of the thin walls, I’d like to use ¼”-32 threads for the touch hole, but don’t see a drum with those threads.

Any  input or ideas?  I’m leaning toward no!

/
    But what caliber is the barrel?

[rich pierce]

The challenge here is the stress put on the threads of a drum with the hammer strikes. It’s challenging to really support the drum with the lock cutout 100%. A 1/4” hole has about 45% the area of a 3/8” hole.

[Clint]

The customer is almost never right.

[smallpatch]

Thanks Taylor,
That’s exactly what I just told the client...... buy another barrel.

Don’t want something out there that’s dangerous.
I appreciate the confirmation.

[D. Taylor Sapergia]

that's your best bet Dane.  It's one thing to build and use a percussion drum with such a thin barrel wall, but quite another to be removing it, installing a drum and then going back the other way.  Those threads will lose too much of their support strength in that process to make the idea of conversion a good one.

[Daryl]

I think this conversion would work perfectly if made up on a patent breech, however, changing back and forth would eventually weaken the 'link'.
Too - what vent would you use? - Too many minuses, not enough pluses.

[jerrywh]

We know that it is a 3/4" barrel but what is the bore? That does make a difference. There are other ways to do this.

[Bob Roller]

Once upon a time I had a 1/4x80 tap and die and they now reside in Western Canada so
a 1/4x32 seems coarse but neither should be use on a drum in a thin wall barrel.
Bob Roller

[Metalshaper]

any way to use a breech that would allow for A bit of a chamber at the touch hole/drum location? This way you could increase the wall thickness in that area and have a bit more secure
hold and support for the drum? a 1/4" threaded drum absolutely requires that the drum be supported by the lock plate. In essence you'd only need the chambered breech with the percussion?

just spit ballin' and I'll slide back and let my Betters offer real advice!

Respect Always
Metalshaper/Jonathan

[okieboy]

 Personal opinion here. Everyone seems to talk about how much thread engagement there is, I.E. how long would the drum thread end up, but more frightening is the wall thickness of the drum. The minor diameter of a 1/4-28 thread is .207", if the drum's flash hole is .093", then.207"-.093"=.114". .114"/2=.057" wall thickness in the drum at the stress point where the drum meets the barrel. .057", less than 1/16" is not much to depend on.

[Metalshaper]

Personal opinion here. Everyone seems to talk about how much thread engagement there is, I.E. how long would the drum thread end up, but more frightening is the wall thickness of the drum. The minor diameter of a 1/4-28 thread is .207", if the drum's flash hole is .093", then.207"-.093"=.114". .114"/2=.057" wall thickness in the drum at the stress point where the drum meets the barrel. .057", less than 1/16" is not much to depend on.

Couldn't agree more, that's why I stated it has to be supported by the plate if it's a 1/4 X ? thread.. using a chambered breech like I described, the builder could make it with a more substantial thread size and gain a bit of safety factor.. and I'd still recommend supporting the drum with the plate..

[jerrywh]

You never did say what the bore was. Also what is the width of the barrel flat.  These must be considered but there is a way, IE. Lengthen the breach plug and extend it past the touchhole far enough to where the drum threads will go through the side of the breech plug and barrel, then make like a 1/4" powder chamber in the plug. That will give you enough thickness for a safe drum thread.
 To compensate for the small diameter of the drum thread just use some good steel for the drum like 4140. you can make the drum out of a Grade 8 bolt but don't harden it unless you temper it.
You won't be able to remove the breech plug with the drum in but you need to sacrifice something to get what you want. You could also change the style of the breech plug so that the touch hole is in the side of the plug instead of the barrel. Some Manton pistols were like that. Comprendo?

[t.caster]

My first ML'er was a kit rifle percussion 13/16" barrel .45 cal. I later converted it so I could shoot perc. or flint matches. It didn't take very many swaps between a vent liner and  drum for the drum to loosen up so much the nipple would rotate back and forth with the wind. A very unsafe condition I figured! I retired that barrel put a new flintlock only barrel in it.
I strongly advise against making a "convertible" rifle!!! Unless you can get two identical and interchangable barrels installed, one perc. and one flint. Why not just build two different rifles??

[jerrywh]

I must admit, it still sounds a little hairy.  You will need a lockplate that will support that drum besides what I recommended previously.