Smoothbore barrel wall thickness

[kutter]

Speaking in terms of cartridge shotguns,,the general accepted wall thickness at minimum is about .013".
I say 'about' because there is no real minimum for proof purposes.
If you send your damascus bbld beauty away to the London proof house to be re-proofed for current smokeless loads,,and this is done routinely,,bbl wall thickness is what it is and it either passes or fails.

Pitted, dented or otherwise damaged or repaired walls will fail the 'view proof' and will not even get to the firing proof phase.

Tissue paper thin walls and otherwise scary thin walls are like wise to fail the view proof when simple measurements normally applied show them to be as such.

A jug choke/muzzle choke  area shouldn't need any more than .015"+ on a side wall thickness on a muzzleloader after the choke is cut. So figure how much you want to remove on a side and add it to that for a total wall thickness at the muzzle.
Jug choking is good for an IC, maybe IC+.
 Trying to get more than that from a jug choke is nearly impossible. You have to get into restricting the actual bore at the muzzle for a couple inches for more choke if you want more but then the loading gets tougher.
Winchesters Patented Skeet Choke was nothing but a jug choke in their M21, M12,ect.
Check some of those bbls out for muzzle thickness sometime. Not much there,but not much pressure either..

[Bob Roller]

Speaking in terms of cartridge shotguns,,the general accepted wall thickness at minimum is about .013".
I say 'about' because there is no real minimum for proof purposes.
If you send your damascus bbld beauty away to the London proof house to be re-proofed for current smokeless loads,,and this is done routinely,,bbl wall thickness is what it is and it either passes or fails.

Pitted, dented or otherwise damaged or repaired walls will fail the 'view proof' and will not even get to the firing proof phase.

Tissue paper thin walls and otherwise scary thin walls are like wise to fail the view proof when simple measurements normally applied show them to be as such.

A jug choke/muzzle choke  area shouldn't need any more than .015"+ on a side wall thickness on a muzzleloader after the choke is cut. So figure how much you want to remove on a side and add it to that for a total wall thickness at the muzzle.
Jug choking is good for an IC, maybe IC+.
 Trying to get more than that from a jug choke is nearly impossible. You have to get into restricting the actual bore at the muzzle for a couple inches for more choke if you want more but then the loading gets tougher.
Winchesters Patented Skeet Choke was nothing but a jug choke in their M21, M12,ect.
Check some of those bbls out for muzzle thickness sometime. Not much there,but not much pressure either..

I'll betcha that Winchester used steels proven in use for gun barrels at that time.

Bob Roller

[kutter]

Point being?


 

[little joe]

Kutter Is that thirteen thousands or one hundred,thirty thousands?

[jerrywh]

 Anybody who has turned shotgun barrels knows that thin wall barrels are very hard to turn because of vibration.  I would not go as far as to say .013 wall thickness was OK. If nothing else they would dent extremely easy. The gauge also has a lot to do with it as well as if it intended to shoot round balls as well as shot.  A 410 or a 32 ga, Has a lot more pressure to deal with than a 12 ga.

[ShutEyeHunter]

My pre WW1 Win M-12 has a muzzle thickness you could shave with, but I digress

Im planning to jug choke my 16 bore and figured Id just start a gentle taper at the waist and hone out metal sort of parallel to the flair.  Leaving it bore diameter for the last 1.5 inches.

Maybe your machine shop could start a bit downstream of the flair

Given the slow rate of metal removal of the hone and my love of the patterning board, Ill plan to report back in a decade or so

[kutter]

Kutter Is that thirteen thousands or one hundred,thirty thousands?

.013" /thirtheen thou.
Some will feel threatened at .013 but safe when the mic reads .015. Go figure.

The thinnest area in the shotgun bbl will be at the waist (just ahead of the forend) in most any commercial round shotgun bbl you find hanging on a semi, pump or even a SxS shotgun.
Use a wall thickness gauge and check a few, you can see it yourself.

I don't care for the bbl's being that thin in that area and won't play with them if they mic in the range there. I like at least .025  for a minimum there. But others don't mind them like that and if sent off to Merry Olde England for a proofing, a shotgun bbl (damascus or steel) w/a wall thickness of .012/.013 at mid length will go thru proof with everything else.

At the muzzle they can be .013/.015 with no problem.
To put SK or IC jug choke in a bbl like that you only take .001/.0025 out of a side.
The wall is still thicker than the walls of some shotguns that have screw-in choke tubes installed.
Trying to put more than an IC choke in by this method doesn't work well in my experience unless the section is extremely long. The work then isn't worth the results which don't meet expectations anyway.
Better to simply back-bore the bbl and get the choke you want that way in a cartridge gun. Not a good option in a M/L unfortunately.
 
Ever see some of the paper thin walls that the 'thin-wall' choke tubes are installed in. Crazy stuff.
But unless someone  doesn't secure the tube right or puts steel shot through a non-steel shot choke tube,,they work fine. No blowups from pressure ripping the bbl apart.

Sure it's in steel that's other than the 12L14 normally used in M/L bbls. But the pressures are supposed to be that much higher.
There's not much pressure  left at the muzzle, even w/smokeless. It burns fast in a shotgun w/a reason.
12ga smokeless breech pressure is around 12,000psi for most over the counter loads.
BP runs about half that.

No need for extra super thick muzzles.

[JCKelly]

Wow.

[Mike Brooks]

Yep, pressure is all but gone at the muzzle, I'd choke that 12 bore colerain barrel and not have any worries....'course I don't worry about as much stuff as most of you guys do.