Should I convert a Cap to Flint?

[Artificer]

I think Bart,Sr called it correctly, though I would still use Dykem on the face of the threaded plug to make absolutely sure. (I believe in double and triple checking things.)

This would also explain why once the patent breech was pulled after having been crushed down against the barrel, it could go a half flat further than before when tightened down, because the threaded plug was not contacting the inside of the barrel breech to keep it from turning further ”“ as I wrote in my earlier post.

So now you have a decision to make on whether you want to stick with percussion or go flint. Either you need to fix or have this percussion patent breech fixed to use the smooth barrel ”“ or fit a new Flint patent breech to the smooth barrel. Either way there is some repair work or fitting that has to be done.

To fix the percussion patent breech and to repeat ”“ A shim can be machined to get the face of the threaded plug to bottom out on the shelf inside the barrel. Then it may be possible to peen/upset metal on the face of the patent breech face forward to close the gap between them. It may not be though, if the gap is too large between the rear of the barrel and the front of the patent breech. If the gap is too large, then another shim would have to be added between the barrel face and the patent breech and filed to fit the outer dimensions of the barrel. However, if you can’t do that work or have it done for you by a friend so the cost does not get real high, then correctly repairing the barrel to shoot percussion would involve fitting a new percussion patent breech.

To convert it to Flint, you would have to fit or have a new patent flint breech fitted.

That’s the way I see it, FWIW.
Gus

 

[MSW]

Gus, I'm leaning in your direction. In hindsight, there probably was a shoulder on the rifling side , but then the barrel went from a .54 rifle (with lots of rust and crud) to a .62 smooth (with no rust or crud of any kind, but a good bit less material) ... so now I've figured out where the shoulder went ...

Arithmetic dictates a shim between the plug and the very back of the barrel at 20 threads per inch, so 1/20 = .05, and .05/8 (eight flats) = .00625, and half of that ('cause it's about half a flat out of time) comes out to .003125 ... about a thickness of a piece of copy paper ... darn!! do they even make shims that thin?

the flint plug at Track is looking better and better ... just have to check that it's the same length as the percussion plug I have now ...

:hmm: :hmm: :hmm:

 

[Artificer]

Well, they make steel shim stock as thin as .001," but I think we may be getting a little ahead of ourselves. I hope I can explain this so it is clear.

There is needs to be a "crush factor" of the metal that you have to figure in when doing the math for either shim. IOW, the thickness of each shim has to be more than just enough to fill up the open area between the threaded plug and the inside of the barrel shoulder AND the face of the rear of the barrel and the patent breech. The shim needs to be a bit thicker than just the open space, so when you tighten down the parts, they will squeeze the metal shim between them a little bit. The shim between the threaded plug and the inside of the shoulder of the barrel does not need to crush much and some folks may suggest not at all, but I think it will need to crush down a little. You will need more thickness on the shim between the rear of the barrel and the front of the breech, so the breech takes some torque or force to draw it up into place. This torque or force that is needed to pull/draw the patent breech tight is what will hold the patent breech securely in place when the gun is shot, so the patent breech won't come loose and begin to unscrew.

Original barrels have been found with copper or even lead shims between the inside shoulder of the barrel and the face of the threaded plug. This was the "period fix" when the threaded plug was too short. I would not use a lead shim and if I chose some other than steel for that shim, I would probably use brass for that shim. However, I would use steel for the shim between the rear of the barrel and the patent breech, because that shim needs to be crushed more and retain it's thickness after crushing.

Before I go further, I have to admit I have never done such shim work on a muzzle loading barrel. I have shimmed modern barrels so the barrel would tighten correctly against the receiver and yes, sometimes with shims only a few thousandths thick. I have also done a LOT of work with round "doughnut" shaped steel shim shims between a barrel shoulder and a front band to get a lock to tighten down with just the right torque. Shims for that normally range from .003" up to .035," as needed. One thing I need to pass on is the thinner the shims, the easier it is to crush them AND crack them if the shims are too thick when they down in the few thousandths of an inch thickness range.

The one thing I can suggest about doing such shim work on a muzzle loading barrel as required for your patent breech and barrel, is you are almost certainly are in for some to a great deal of "trial and error" before you find the size of shims that will work for each application.

After looking at the pictures you provided, I personally would think about at least trying a new patent breech in either percussion or flint before I tried shims. IF you only hand screw a replacement patent breech into your barrel to check it and do not cut/file/grind on the new patent breech, you probably would be able to return it for a refund if it won't work. (I would suggest asking about that before you purchase a new patent breech.) THEN if the new patent breech won't work for how you want to use it, then I would start working with the shims.

Gus

 

[MSW]

Gus, thanks for the post ... I appreciate your expertise, and I also appreciate your taking the time to explain this stuff to someone who's not in tune with metal as much as I should be.

I'll go with the new breech plug in flint, I think.

Again, thanks for your patience!

 

[Artificer]

You are most welcome.
Gus

 

[M. De Land]

Gus, how about taking .045 off the back of the barrel and moving the plug up one revolution to TDC,seeing as the breech face does not contact the counterbore shoulder anyway.
I think the single key and tennon could be altered enough to accommodate the length change without moving either and the key head would still cover.
The under rib would need shortening that amount at the rear as well.

 

[Artificer]

That's a good thought, M.D., but unless he has a machinist to do it for him; I think that would be even more of a challenge and/or possible nightmare for him.

Since he is thinking/planning on going flint, I think he should at least investigate trying a new flint patent breech to see if that is the easiest method for him to solve the problem. He still may need to take it to a machinist to fit it, though.

Gus