AmericanLongRifles Forums
General discussion => Gun Building => Topic started by: monro1066 on July 28, 2012, 03:08:57 PM
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New build and an accident..have a 50 cal barrell.
Had 2 friends in shop and didnt pay attention while working.....
cut the B.Plug shortish....and have now 7/16 th (7 threads )
of a Breech Plug threaded the shoulder ,though does not meet
or fit neatly......do I need a new B.Plug and re- cut/re-fit so it is
"snug" to shoulder...........?
Any help is appreciated............................
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7/16" is considered too short nowadays. You do need a good seal else you'll risk gas cutting of your threads. New breechplug would be my choice.
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You don't say what size it is, but one way to fix it would be to fit a dime in front of your plug. You can lightly file or scrape one side flat so it cleans better. A dime is .050 thick and about .704 wide. I think it works on 3/4" plugs. And you could use Thompson Center's "Super Lube, Anti-seize Lubricant" on the threads. This "seals the threads of muzzleloading breech plugs". "Protects threads and other metal surfaces from corrosion."
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You don't say what size it is, but one way to fix it would be to fit a dime in front of your plug. You can lightly file or scrape one side flat so it cleans better. A dime is .050 thick and about .704 wide. I think it works on 3/4" plugs.
The problem here is that a dime on the breech face does nothing for thread engagement. I personally would want 9 full threads on a 18 tpi plug (assuming that's what you have). If its 16TPI I would want a full 8 threads. I have seen original barrels with less but I wouldn't want to shoot them.
Dennis
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A new breach plug is cheap insurance. I wouldnt attempt a salvage of it.
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Hi all...............there seems to be a consensus from some
good back ground knowledged folks.
Time to buy a new plug..........and fit it when I am concentrating.
Thanks guys for the replies
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Hi all...............there seems to be a consensus from some
good back ground knowledged folks.
Time to buy a new plug..........and fit it when I am concentrating.
Thanks guys for the replies
Mechanical advantage rule demands no less than 50% in length, so fit a new plug and sleep better at night and no wife abuse needed. ::)
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Hi Rodger.........advice on any thing re a happy wife is
always welcome too..........Fitting a rifle barrell Breech plug
though ,I believe, is by far and away simpler to understand.....
and yes, I made a mistake on that too.........lets just let humour
rule this time :)........Regards to all who helped
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Hi Rodger.........advice on any thing re a happy wife is
always welcome too..........Fitting a rifle barrell Breech plug
though ,I believe, is by far and away simpler to understand.....
and yes, I made a mistake on that too.........lets just let humour
rule this time :)........Regards to all who helped
When Mama is happy every one is happy!! Bob
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well said Rodger
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Guys,
The most important thing in any thread engagement is not the number of threads but it is the radial strength of the female part. In a standard coarse thread nut there are three threads which is strong enough to break the bolt if both bolt and nut are of the same strength. A heavy nut is much stronger than a standard nut, yet it still has the same three threads - it is thicker across the flats to resist failure by dialation.
So, when we breech a barrel we must pay close attention to the thickness of the barrel breech wall thickness. For instance, if we use a 3/4 thread breech in a barrel that is 15/16 leaving a 3/32 wall - an overpressure could cause the breech joint to fail by dialation. The pressure expands the barrel diameter and decreases the thread radial engagement resulting in a much weaker joint, and a potential failure. So try to keep a breech plug thread that will give a stout wall thickness while still sealing the bore end on a shoulder. Does this make sense?
As for me, I make the breech plug 9/16 long, giving about 12 threads. That is 18th c style threads.
Jim
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That does make sense so thanks for that.D