Bore/barrel size

[tallPercshooter]

I've observed that most modern, quality black powder barrels have wall thickness of around .20. I have seen a 13/16 barrel with a .50 bore. That would be .81 - ,50 = .31 /2 = .15.5 barrel wall. Would this be safe with moderate powder charges and patched round ball? Seems to be cutting it close.

 

[tenngun]

Seems a mite thin to me. However I would note. Ball doesn’t take too much pressure to run down a bore.
Pressure is going to go where it’s easiest to go. What’s easier, breaking steel or pushing the ball out
Dixie put 300 grains in a pistol barrel and set it off with both ends plugged
Gas’s exit via the touch hole was easier then busting barrel.
Sam Fadala loaded a one inch .58 with five hundred grains and three minnie ball without a bust.
I would feel uncomfortable shooting such a gun but bet it can handle 60-90 grains 3 f without a problem

 

[Sean E Bug]

i don't have any numbers but I do know many rifles get built with the lugs soldered on because the swamped profile makes parts of the barrel to thin to have a dovetail.

 

[The Appalachian]

Modern barrel steel is light years ahead of period correct wrought iron that's hammered into shape around a mandrel and forge welded together at the seam. That said Bobby Hoyt has a minimum wall thickness he goes by on re-bores, and that's for good reason. 150 thousands is way too thin in my opinion.

 

[SDSmlf]

I've observed that most modern, quality black powder barrels have wall thickness of around .20. I have seen a 13/16 barrel with a .50 bore. That would be .81 - ,50 = .31 /2 = .15.5 barrel wall. Would this be safe with moderate powder charges and patched round ball? Seems to be cutting it close.

A few OEM barrel makers have produced barrels with .170” wall thickness or so (outside diameter less bore diameter and rifling depth) but they controlled every aspect of the barrel manufacturing. Most folks boring barrels seem to want .200 minimum wall thickness. That takes in rifling depth and includes dovetails and tapped holes for sights and such. Go less and you are on your own in my opinion. And yes someone will come along and claim a thinner number will work or as worked for them, but it’s unlikely they will be a current custom barrel maker or someone who rebores them for a living, let alone accept financial liability if things go south.

 

[Phil Coffins]

How thick is a 12 gauge shotgun barrel?

 

[tallPercshooter]

Smokeless shotgun barrels are much thicker at the breech, thinner at muzzle. Black powder doubles the same. I had a Mowrey 12 ga where the barrel was the same thickness at breech as at muzzle. Never had any trouble with sensible loads.

 

[Sandro_Ventania]

But how thick?

 

[tallPercshooter]

I no longer have the Mowrey. But I would say it had a one inch barrel. 1.0 - .72 (12 ga) = .28 div by 2 = .14 barrel wall thickness. Just over 1/8 inch.

 

[Col. Batguano]

Right you all are, but modern guns are made with modern steels. Many of out ML'ing barrels are 12L14 steel, which isn't as tough.

That said, a cut-in barrel lug or sight is going to have most of that cut away steel replaced by the lug base, so much of what is lost is then replaced. If you solder the lugs back in place I'm guessing most all of the lost strength is regained. As the thinnest part of the barrel is the mid point of the barrel flat, there will also be something of a "spine" put there as well which is the vertical part of the barrel lug. Soooo, all that said, in several places on the forum I've seem 0.008" mentioned as the absolute minimum, but 0.010" and 0.012" are mentioned more often.

You also have to remember that the further you get down the bore, the lower the pressure will be. Ex; a 24" M1 Grand starts at ~48,000 psi at the breech, but that pressure has dropped to <5000 psi 22" down the bore (5% of breech pressure) where the gas port is. Most of our heavy loads with BP don't generate much more than 20,000 psi (at the breech), so assuming a level linear pressure drop as you go further down bore you can do the math at your target location as to your expected pressure.

It's for subjects like this that I really wish Zonie's was around to answer them. He had all the metallurgical data and fail point pressures right at his finger tips. If you research some of his old posts you may get some more educated data.

 

[The Appalachian]

in several places on the forum I've seem 0.008" mentioned as the absolute minimum, but 0.010" and 0.012" are mentioned more often.

You probably want to move some decimal points there......

 

[Nobade]

I don't know but my TC Cherokee 45 caliber kind of gets me nervous when the charges get too big. I don't think I'd want that rifle to be a 50 caliber. But I do understand that the factory has tested them and says they work so I'll trust that. They have 13/16" barrels.

 

[Sandro_Ventania]

I don't know but my TC Cherokee 45 caliber kind of gets me nervous when the charges get too big. I don't think I'd want that rifle to be a 50 caliber. But I do understand that the factory has tested them and says they work so I'll trust that. They have 13/16" barrels.

But why would you be nervous? A 13/16, .45 caliber barrel is 0.18 thick. sounds good!

 

[Col. Batguano]

You probably want to move some decimal points there......

Oops. You're right! My mistake. The correct numbers are; 0.08", 0.10" and 0.12" Sorry if it caused confusion.

 

[Nobade]

But why would you be nervous? A 13/16, .45 caliber barrel is 0.18 thick. sounds good!

Hi over here Sandro!
I know it's safe, TC says so. But that is still a very light rifle to be loading up very heavy. I certainly would not want one in 50 caliber. It is, however, very nice to carry all day chasing after deer.

 

[tallPercshooter]

But why would you be nervous? A 13/16, .45 caliber barrel is 0.18 thick. sounds good!

Zillions of .45 13/16 inch octagon barrels out there. Pretty standard.

 

[James Kibler]

I assume you are referring to a straight octagon barrel? In this case, one big thing to consider is the wall thickness around the breech plug threads. With a swamped barrel where the breech is larger, most barrel makers are perfectly fine with .100" wall or even thinner.

 

[Sandro_Ventania]

Presumo que você esteja se referindo a um cano octógono reto. Neste caso, uma coisa importante a considerar é a espessura da parede ao redor das roscas da culatra. Com um cano inundado onde a culatra é maior, a maioria dos fabricantes de canos fica perfeitamente bem com parede de 0,100 "ou até mais fina.

Você conhece algum teste que mostre qual espessura não suporta uma carga normal de pólvora negra? Eu me lembro, quando era adolescente e fazia uns "brinquedos" improvisados com barris de apenas 0,07... vivo para contar... mas não sou mais adolescente para correr riscos... ha ha ha!

 

[The Appalachian]

cuidado, você pode arrancar os olhos fazendo coisas assim.

 

[Sandro_Ventania]

cuidado, você pode arrancar os olhos fazendo coisas assim.

Sim...eu fui um adolescente irresponsável...como acho que a maioria dos adolescentes é!