breech plug length

[gene mosier]

hi folks-i'm finaly gettin started on my pistol.i bought a 7/8x12 inch barrel and an r.e. davis lock that resembles a becky. the barrel's threaded 5/8 18 and 5/8 inches long.thats too long for my lock without using the bridle screw for the rear lock screw. my question is, if i shorten the plug length to 3/8(which is perfect)will that be strong enough? older guns used about that length with a courser thread. BTW its a 50 cal.

 

[paulvallandigham]

In general a modern steel Breech plug that is 3/8" long will be strong enough to resist the pressure put in the back of the barrel, particularly if you are going to build a flintlock.

Some original guns have been found with plugs as short as 1/4 inch, with a much coarser pitch.

MY personal decision would be based on seeing 3 complete threads( or more) left on the shortened plug end. If you have at least 3 full threads, you should be okay. With 18 threads to the Inch, as on your plug, you should have 6.75 threads showing on the threaded end of the plug when its 3/8" long. ( 18 divided by 8, times 3 = 6.75. )

If there is space at the back of the barrel, before the threads begin, you may have to shorten the back end of the barrel to make the face of the plug fit up snugly against the bore, and rifling.

 

[gene mosier]

thanks Paul. having someone elses opinion takes some of the worry out.is this a common problem with this small of a lock?

 

[paulvallandigham]

Yes, and NO. Actually, I think its a common problem with all barrels and plugs. The barrel makers leave extra threads, and metal at the back of the barrel, because they don't know whose Tang and Breech plug the buyer is going to use. The Breech plug makers leave extra length and threads on the plugs, because they don't know what barrel you are going to put on their plug, much less caliber, smooth or rifles, ROT, Drum or patent breech, flintlock, underhammer, Mule Ear, or a dozen other things that matter.

And, sadly, most builders DON'T realize that this is the most important part of fitting any barrel and plug to a given action- adjusting that length, as you are doing. So, it becomes a problem when people build the gun, and then find themselves drilling angled hole in the face of the breechplug face to get to their vent hole, or have to cut back a vent liner to save the threads on the plug, that extends to far forward, or do the same dance with a drum and nipple gun. My brother learned this the hard way with the first underhammer rifle he built. :shocked2: :thumbsup: Luckily, he addressed the problem before he put keyways or hangers in his barrel to carry the forestock.

 

[gene mosier]

wasn't sure i was going about correctly,just new things weren't working out.do all your lock fences line up with the barrels? pistols for my nephew,so i was a mite concerned.

 

[paulvallandigham]

Yes, and no. When the barrel/plug is not fitted properly, you get all kinds of different locations for the fence. When everything is done correctly, and IF that is the correct sized lock for the barrel, then the fence should line up with the bark of the barrel. :thumbsup:

 

[Stophel]

I'd go for about 7/16". :wink:

The plug can be notched for the touch hole, if required, though for one that short, it shouldn't be.

It's nice if the pan fence meets up with the breech end of the barrel, but if it's forward just a little, it would only be like a huge number of original flintlock guns. :wink:

 

[Capt. Jas.]

I'd go for about 7/16". :wink:

The plug can be notched for the touch hole, if required, though for one that short, it shouldn't be.

It's nice if the pan fence meets up with the breech end of the barrel, but if it's forward just a little, it would only be like a huge number of original flintlock guns. :wink:

+1

 

[Stophel]

Now the English did begin to get really anal about having the rear of the pan line up with the barrel breech...so they stretched the pan fence back to meet the breech, not really moving anything around.

 

[gene mosier]

just like the Jim Chambers locks. 3/8 is all i can stretch out of the bolster. its either that or the bridle screw hole. lock has a rear fence screw that mite work exept its drilled & threaded at 90 degrees to the lock. what i need is a slight up angled hole to thread.theres just enough room behind the fence scew to do that with a 3/8 plug.was just hopeing that the plug was stong enough.

 

[Stophel]

I'm not real crazy about the "Becky" lock. But, if you got it already, you can make it do.

 

[gene mosier]

thank all of you for your advice and comments-gene