Re-bore a Lymans GPP

[KW]

I have stumbled across an old Lyman .50 cal great plains pistol kit and was wondering if it was possible to have the barrel re-bored to a .58 cal? If I took my measurements right it is 15/16 across the flats. I would even be fine with it being a smooth bore .58 if that would be a safer way.

 

[mazo kid]

Others with more knowledge than I hopefully will answer. My opinion is that the bore to .58 caliber would not be a safe move. Do the math....58 cal = .625". 15/16" = .937". Barrel wall thickness would be .312 divided by two, or 0.156". Seems a little too thin for my taste. Emery

 

[Blizzard of '93]

with a light load under a prb it would 'likely' be OK but .54 would be safer.

 

[mazo kid]

OOOPS! My mistake, I was using 5/8" instead of .58 caliber. Still, barrel wall thickness would be ~.178; I would consider it still a teeny bit thin. Emery

 

[Zonie]

It would depend on the size of the breech plug threads as well as the final wall thickness.

If the breech plug had a 5/8-11 thread, the minor diameter of that thread would be .542. Boring the barrel out to a .58 would remove some of the threads material weakening the threads.

Actually, the question comes down to how much money do you want to spend on a Lyman pistol?

Reboring a barrel, even with a smooth bore is quite expensive. Usually well over $100.

 

[KW]

Well shoot was hoping it was going to be possible. Oh well. On to the next idea I guess :wink: