Cutting a Breech Plug

[hawkeye2]

A 5/8 jam nut is 3/8" thick, thinner than a standard nut. A nut can be used as a file guide to insure the plug face is square to the threaded area.

 

[user 34300]

I do not get the perceived issue here. File the plug to the required length. Chase the last thread with a 3-corner file to clean it up. Done. IF it does not start in the barrel figure out why. Filing it with a nut installed will not do any thing useful. You will need to spot the face of the plug to fit he internal barrel shoulder either way.

 

[HighUintas]

If filing off 1/4" of a breech plug is easy I'll just go that route. I don't think I've seen 3/4-16 nut available at the hardware store before

 

[hawkeye2]

3/4-16 is the standard fine thread while 3/4-10 is coarse thread. A 3/4 jam nut is approximately 7/16 thick. Fine thread nuts, specially that large probably aren't found in the bins of a lot of hardware stores. I believe the discussion here is about a 5/8 fine thread though unless your breech plug is 3/4.

 

[HighUintas]

Yes I believe the OPs is 5/8. Mine is 3/4

 

[geb324]

File it down more time consuming but more accurate.

 

[Eric Krewson]

Seems like the last GM barrel I used had a 5/8" thread for the breechplug, for lock fence alignment and having the liner off the breechplug I like them shorter, more like 1/2". A file, small square, bottom tap and some marking blue and I had the barrel and the plug filed down as well as plug seated properly in a few hours. I never get in a hurry on a project like this so it takes me longer to do a good job.

On my first build somehow I cut off the stock too short which left me with 1/2" too much barrel sticking out past the nose cap. A hacksaw, square and a file got rid of this extra 1/2".

This is the end result from long ago, I made a homemade crowning tool to finish my crude work off.

 

[HighUintas]

Seems like the last GM barrel I used had a 5/8" thread for the breechplug, for lock fence alignment and having the liner off the breechplug I like them shorter, more like 1/2". A file, small square, bottom tap and some marking blue and I had the barrel and the plug filed down as well as plug seated properly in a few hours. I never get in a hurry on a project like this so it takes me longer to do a good job.

On my first build somehow I cut off the stock too short which left me with 1/2" too much barrel sticking out past the nose cap. A hacksaw, square and a file got rid of this extra 1/2".

This is the end result from long ago, I made a homemade crowning tool to finish my crude work off.
View attachment 120847

What do you mean by Lock fence alignment and having the liner off the breech plug?

 

[longcruise]

I just put the ta g i. The vice and whack it off with a hacksaw. Leave a little bit to clean up with files.

 

[Eric Krewson]

With 5/8" of threads on a GM barrel the back of the barrel won't line up with the lock fence and still have the front of the plug where it needs to be for liner instillation, you have to move the barrel back some.

I cut 1/8" of threads off the plug and the same off the barrel so the lock fence would line up with the back of the barrel, just for looks, either way works just fine. I just checked my other flintlocks, some line up like this and some don't, depending on the lock size, all work just fine.

Here is the same rifle finished, just took the picture, I just like the looks of the fence aligned with the back of the barrel.

This is the lock alignment on my precarve from hell rifle, the lock inlet was already cut, not much I could do about it.