Breechplug blowby

[topbike]

I have a Jonathan Browning Mtn. rifle that was left loaded for years and of course the end of the barrel and breech plug are corroded. I have removed the plug and cleaned both it and the barrel however when I took it to shoot yesterday I discovered there was some blowby between the breechplug and the barrel face. The threads on the breechplug and barrel look fine but obviously something is allowing it to leak. Any suggestions appreciated.

 

[bubba.50]

if it was me, I'd put a thin layer of J-B Weld on the threads before re-installin' the plug.

but you might feel better usin' a good coat of never-seize or some Teflon tape on the threads.

worse-case scenario, cut an inch off the rear of the barrel & re-install plug. which of course would lead to a couple other mods

 

[Vaino]

Evidently the face of the plug isn't shutting off on the "ledge" at the bottom of the threaded ctbr. If the orientation of the tang and bbl flats is good, then the lack of shutoff could entail a lot of work, some work or no work.

A lot of work comprises removing enough steel from the plug face to achieve a shut off which in this case means a 360 degree rotation and enough steel removal to achieve a plug face seal w/ the "ledge". This would also cause inletting problems.

Some work entails using a nonferrous shim between the plug face and the shutoff "ledge" which would achieve a seal and still maintain the bbl/tang flat orientation.

No work possibly can be achieved w/ repeated shooting in the hope that the fouling will seal the gap. I would try this first and it just might work......Fred

 

[nhmoose]

Lead washer was used historically. Will work today the same.

Don't want lead use a piece of shim stock the thickness needed

 

[topbike]

Thanks for the replies. I thought about a shim of some sort and wondered if a crush washer would do the trick. Where would I get a thin lead washer that would work? Should I take it to a gunsmith to have it done? I am pretty much a black powder neophyte.

 

[Rifleman1776]

Thanks for the replies. I thought about a shim of some sort and wondered if a crush washer would do the trick. Where would I get a thin lead washer that would work? Should I take it to a gunsmith to have it done? I am pretty much a black powder neophyte.

Shims were used. Historically, you will find both gold and platinum. Silver, as from a coin might be OK. If you are handy it is a doable job. Pound the coin thin, cut the hole and screw on the breechplug. If you are not handy in the shop do look for a good gunsmith, preferably one with ml experience. Good luck.

 

[M. De Land]

You need to get it sealed off because your blowing corrosive fouling into the threads and it will cause trouble down the line.
I'd refit a new breech plug if it were mine as I have the shop and tooling to do the job but a copper washer would probably be a good gasket if you don't have the means to refit a new plug.
A copper washer can be cut out and hammered to what ever thickness needed on a make shift anvil and will seat against the counterbore barrel plug ledge, to seal it off.

 

[Zonie]

I might be wrong but I think your rifle uses a snail breech.
If this is true, the hole thru it will need access to the powder charge so you must use a washer type seal.

Until you know how thick the washer needs to be you can't make a good decision about what the best thing to use would be.

If you have a precision depth guage like the one that is built into a vernier, dial or digital caliper, remove the breech plug and measure the distance between the end face of the threaded area and the face that will fit up against the rear of the barrel.

Then, measuer the depth from the rear of the barrel down to the shoulder at the bottom of the threads.
That shoulder is what the seal will press against when the breech plug is screwed in.

If the difference in measurement is only a few thousandths of an inch (.001-.020), some brass shim stock could be used. The shim should be 1 or 2 thousandths thicker than the gap.

If it is more than .020, a thin brass washer might be used.

For instance, if the difference in measurements was .026 you could take a .032 thick washer and sand it down to .027 thickness on a wet/dry black silicone sandpaper on a piece of window glass.

Then, if this is too much to ask, you could wrap a few turns of teflon pipe thread tape around the threads on the plug.

IMO, there is no way you should even consider using JB Weld on the threads.
If you do, it will be almost impossible to ever remove the plug without first heating the area to over 450°F.

 

[M. De Land]

The reason I suggest copper is because it is softer than brass but not as soft as lead and stand up much better to the breech pressure of black powder combustion.
It will be a very malleable and yet tough gasket seal for the need you describe.

 

[Don Steele]

As a fellow "neophyte"...(at least when it comes to building, not shooting)the only thing I might try is the Teflon tape suggestion.
If that doesn't resolve the issue I'd be looking for a qualified gunsmith with blackpowder experience to send it to.
Something isn't right..IMHO this isn't an issue to ignore and just keep shooting.

 

[topbike]

I am certainly not shooting it and will talk to a gunsmith about the various options provided in this thread. Certainly not looking to get hurt or hurt (God forbid)anyone else. Time to practice with my flintlock until I get this fixed. I love the gun and it is extremely accurate but now is the time to go to someone with a lot more experience than me.
Thanks for all the replies.

 

[nwtradegun]

i would recommend using rector seal hardening type. it is used on all forms of piping. stands up to high pressure steam it forms a seal better than a gasket.

 

[wulf]

Take it to a gunsmith and tell him to fix it...

 

[Follett]

How tight was that breech plug? I've always heard they were next to impossible to remove. I have a JBMR, that would show oil on the top flat of the barrel, after a few shots, it would disappear. At any rate, no JB-weld for sure.

 

[Rifleman1776]

The reason I suggest copper is because it is softer than brass but not as soft as lead and stand up much better to the breech pressure of black powder combustion.
It will be a very malleable and yet tough gasket seal for the need you describe.

I believe copper or brass would react with the steel and chemicals to cause corrosion in the breech area. Neutral metals like gold would not have this effect. A silver coin would cost under $20.00 and leave an attractive line where the plug/barrel meet.

 

[M. De Land]

I doubt any chemical action would develop but it's possible.
Where talking about the inner shoulder at the plug end inside the barrel which would not be visible after installation.

 

[Zonie]

I believe Rifleman is speaking of possible galvanic corrosion due to the dissimilar metals in contact with each other with an electrolyte like water present.

Referring to a chart which shows combinations of metals that can cause trouble and using carbon steel as one of the materials, poor selections for a seal would be made from Magnesium, Zinc, Aluminum, Cadmium, cast iron or stainless steel.

Good materials would be copper, brass, bronze, lead and silver, to name just a few.
http://www.structx.com/Material_Properties_001.html

 

[ol vern]

Good information.

Thanks Zonie

 

[ohio ramrod]

an old, all cooper penny, can be clamped between two pieces of soft wood,, unclamp and find the center of the impression, mark the center and drill a small hole through to give center from the other side, reclamp the penny and drill out center, put penny on small bolt if needed and chuck into a drill and use a file to get O.D down to size if needed. If too thick Push over a file to reduce thickness. This will make a "soft washer'. So you see while a lathe would be easy a "spacer washer can be made with simple tools and a lot of patience. :idunno:

 

[Zonie]

Good idea.

That would make a cheap drill jig.

Not much good for a production run of 1000 parts but it sure would work for a couple.