Breech plug issue

[Eric Krewson]

I bought a barrel for a TN bear pistol second hand, it is a 15/16 barrel in .54, when I was measuring for the plug depth to buy a breech plug, I noticed that the breech was bored a little off center, the breech is threaded for a 5/8 18 plug. There is hint of a shoulder on one side of the breech and none on the other side, just rifling.

I have a friend who could probably recut the breech for a 3/4 16 plug, would this larger plug be safe in a 15/16 barrel?

 

[FlinterNick]

I bought a barrel for a TN bear pistol second hand, it is a 15/16 barrel in .54, when I was measuring for the plug depth to buy a breech plug, I noticed that the breech was bored a little off center, the breech is threaded for a 5/8 18 plug. There is hint of a shoulder on one side of the breech and none on the other side, just rifling.

I have a friend who could probably recut the breech for a 3/4 16 plug, would this larger plug be safe in a 15/16 barrel?

I would return the barrel, i had that issue with a track of the wolf fowler years ago, the barrel wall was much thinner on one side than the other.

 

[Eric Krewson]

I bought it from a nice older gentleman who I suspect never noticed the problem, I don't know if returning it is possible. I sent him an email today to ask his opinion.

 

[rich pierce]

With it off center the thickness of the barrel on one side may be marginal when you go up a size in breechplug?

 

[FlinterNick]

With it off center the thickness of the barrel on one side may be marginal when you go up a size in breechplug?

The biggest concern for me would be how close the rifling is the outer barrel wall, while it’s likely never going to be an issue. Now, it could be down the road.

I’m skeptical of barrel issues, if i can’t satisfy my skepticism on a barrel issue, then i send it off to either be lined or copied.

 

[FlinterNick]

I bought it from a nice older gentleman who I suspect never noticed the problem, I don't know if returning it is possible. I sent him an email today to ask his opinion.

How much taper is on the barrel, is it a fast or slow taper ?

I had a barrel sent to me with an over filed flat, it was so over filed that there was hardly any barrel wall at the breech end, i recommended that it be replaced for $250.

I see a lot of overloaded guns at re-enactments, and it only takes once incident to change all the rules today.

 

[Rich44]

If it would leave enough barrel by cutting and boring correctly I would keep it. If not I would tell myself it was wonderful for me to help out this older gentleman and move on with a smile. To use as is or with a larger plug creating thinner wall would always be on my mind.

 

[The Crisco Kid]

I assume you're talking about the inside shoulder where the plug meets the barrel. If it looks like a good crush fit on the shoulder it should seal and should be ok. The off center should be up or down and not side to side or the sights will be off center too. That's if it's the barrel that's off. If it's the plug threads that are off that may not affect the sights.

 

[Eric Krewson]

I got out my Teslong for a closeup picture. On close examination there is no shoulder in the breech except for a small hairline on part of the breech. By off center we are talking about 1/32nd or less. What looks like a shoulder is the last thread, there is a little shoulder showing at 3 o'clock, none at 8 o'clock.

 

[ZUG]

As this is a pistol it will not see the same pressures as a rifle. This is a tough call. You want to be safe and not build something that would be dangerous to you or others around you. If it was me I'd use it but not load it with heavy charges. I also would not sell it to someone. I would just hold on to it.

 

[Scota@4570]

I had a similar situation. The 5/8" thread leaves little barrel seat in 54 caliber. After consulting more experienced folks I was told it is OK. So, I pushed my concerns down deep. It is the way it is normally done by barrel makers.

The 3/4" threads would leave too little meat in the barrel. So I considered going to M17 x 1.5. That might have worked out but I would have had to make a breech plug from scratch.

The problem is fouling in the threads? So, I heated the plug and barrel up enough to melt allox bullet lube and coated the threads inside and out then installed the plug. No fouling can enter the space now, there is not space to enter. I am sure any heavy grease or wax would have worked out too. I suppose one of the thick Loctite products would do the same but I think that is overkill.

 

[2 shots]

douglas used to make most of their barrels like that!!!! only XX were bored center.

 

[The Crisco Kid]

As mentioned, I'm thinking this might be the place to use a little Loctite.

 

[Eric Krewson]

My gunsmith friend can make any breech plug, his specialty is building B/P bench rifles from scratch

On my first rife my plug to breech face fit was suspect, I put so much high temp anti seize on the threads that no fowling or water from cleaning gets down in the threads. I have pulled the breech plug on this rifle a bunch of times the threads are always fowling and corrosion free.

 

[Barry Strickland]

Eric,
You can go to TOW and buy a breech plug that is made for a 15/16 barrel that has 3/4 x 16 threads.
In truth I don't see a real problem with the way it is now in the pistol barrel.
As you said the anti seize on the threads works well in this case.
Also, if you have looked at many original breech plugs and threads, the ones we use now are tremendously stronger.
Barry

 

[ZUG]

I've use teflon pipe tape to seal the threads of some breach plugs. Work great - never had an issue. Also made plug removal easy.

 

[rchas]

I don't see any problem especially as you are going to be using much lighter loads than a rifle. The end of the plug will seal fine against the bore.

Actually, until fairly recently, an off-center bore at the breech end of a barrel was almost a given. You put the thin side as either the top or bottom flat depending on how tall you wanted to make the front sight.

 

[SDSmlf]

If it’s just the breech plug threads that are off center, consider removing the offending threads by shortening the barrel and have your gunsmith friend cut new threads on center. And have you asked your gunsmith friend his opinion? With the barrel in hand, let him make the call.

My gunsmith friend can make any breech plug, his specialty is building B/P bench rifles from scratch

 

[54ball]

I got out my Teslong for a closeup picture. On close examination there is no shoulder in the breech except for a small hairline on part of the breech. By off center we are talking about 1/32nd or less. What looks like a shoulder is the last thread, there is a little shoulder showing at 3 o'clock, none at 8 o'clock.

View attachment 261552

I would use it.
The truth is after the first few shots it’s all going to carbon up.
If you look at original beech pins you’ll see how short and course threaded they are....
Personally.....
I think it’s fine but this is me, not you.

The perfect 1 inch long breech pin sealed and tightened with a 4ft long wrench at 842 ft lbs is modern thing.

 

[BJHabermehl]

I bought a barrel for a TN bear pistol second hand, it is a 15/16 barrel in .54, when I was measuring for the plug depth to buy a breech plug, I noticed that the breech was bored a little off center, the breech is threaded for a 5/8 18 plug. There is hint of a shoulder on one side of the breech and none on the other side, just rifling.

I have a friend who could probably recut the breech for a 3/4 16 plug, would this larger plug be safe in a 15/16 barrel?

If it were mine i wound be not concerned a 5/8 breech plug in a 54 cal.barrel will need to seal at the end of the threads not so much at the shoulder as it’s almost nonexistent any way. When fitting you need to feel the plug scrunching at the end of the threads, as Don Getz explained to me. Blue lock tight would not hurt a thing either at the final assembly. I rather use that than anti seize, it doesn’t migrate and cause browning problems later, and keeps the threads free of corrosion. And the parts still disassemble with normal hand tools. BJH