Barrel boring question

[Rebel]

Do you guys that build think it would be safe to have a 7/8" across the flats .50 cal barrel bored out to a .54 cal/.28 ga smoothbore. I would want to be able to use at least 80 grs of 3f and a patched rd. ball, or 70 grs and 1 oz of shot. Taking into consideration the 2 dovetails on the top for the sights, and 2 dovetails on the bottoem towards the muzzle for the under barrel lugs, would there be enough barrel wall thickness left to be safe with those loads. Thanks for any help and advice.

 

[Swampman]

My personal conviction is that pressures are considerably less in a smoothbore than they are in a rifle. I don't know the answer to your question. It would be very close. Is this a flint or percussion?

 

[roundball]

Do you guys that build think it would be safe to have a 7/8" across the flats .50 cal barrel bored out to a .54 cal/.28 ga smoothbore. I would want to be able to use at least 80 grs of 3f and a patched rd. ball, or 70 grs and 1 oz of shot. Taking into consideration the 2 dovetails on the top for the sights, and 2 dovetails on the bottoem towards the muzzle for the under barrel lugs, would there be enough barrel wall thickness left to be safe with those loads. Thanks for any help and advice.

I have no qualifications to comment on safety of doing that...as a couple of references though, TC's .54 is in a 1" barrel, and GM does make a .54cal in a 15/16" barrel but it's a smoothbore and has no rifling grooves that are cut deeper into the sidewalls...and I assumed that's why they felt OK about making it on a 15/16" blank...dunno.

Have you mic'ed the groove-to-groove diameter of your 7/8" barrel as it is right now?

 

[Rebel]

No i don't have a mic. I have a guy from the forum who says he can do it, but i want to be sure it is going to be safe to shoot afterwards. It is a flintlock if that matters any.

 

[Swampman]

If it's a flintlock, and it has a vent liner, there ain't gonna be much barrel wall to keep it from blowing out. Just a thought.

 

[ss1]

This is interesting. There are a lot of old t/c 50cal pc barrels that should be good for something besides scrap.

 

[Rebel]

This has a patent breech, so the liner goes into the breechplug and not just through the barrel wall. May make a difference. Mostly worried about the thickness under the dovetails. Not planning on shooting very loads in it like i said.

 

[roundball]

My gut says it might not be safe...no science, just the fact that neither TC nor GM offer that in a 7/8" barrel.

And as SS1 just reminded us, there's a ton of .50cal TC barrels out there and if it was a reliable/safe thing to do, seems like it would be fairly common knowledge around forums like this...dunno

 

[Rebel]

Thanks, for the advice. That is what we are here for. Take care.

 

[J.D.]

The smallest barrel diameter that any maker will bore to 54 is 15/16, and for good reason. Do the math, 7/8, or .875-.54/2=0.1675 for the barrel wall thickness.

If you calculate the wall thickness for a 15/16 .54 rifle barrel, allowing for .010 deep rifling, you get .937-.56=.373/2=.1885 wall thickness. That's a .021 difference in wall thickness. That's a lot of metal when one considers the amount of wall thickness we're talking about.

Then ya gotta figure the depth of the dovetails. and how close one might be to the breech?

IMHO, I wouldn't do it.
J.D.