Wall thickness and chamber pressure

[cal.45]

I’ve seen old black powder revolvers with very thin cylinder wall thickness, like these cylinders for example:

and this pepperbox has also resonable thin walls:

Back in the days the quality of the steel was inferior, so it got me to wounder about the steels of today.

What’s the minimum thickness of a chamber (or overall barrel for a pepperbox) in cal .40 containing a 25-30 grain FFFG black powder (or equivalent pyrodex P) load with a 92 grain lead roundball tightly infront of it (+wadding) if it’s made out of a steel with following properties:

Yield strength min [MPa]
700

Tensile strength [MPa]
900-1050

Elongation A5 [%]
12

Hardness
270-325 HB

And how many PSI will such a load described above generate?

 

[yonderin]

As I see it, the advantage of those shorter barrels/cylinders id that the gases may start to vent before maximum pressure spike hits.

In the case of the cartridge revolver the bullet has hardly even moved. Obviously.

Sorry. Can't help you with your actual query.

 

[Col. Batguano]

Have you done some measurements to see how thin the cylinder walls actually are? It would seem to be particularly thin under the locking lug detents. Might as well measure both old style BP guns, and modern high pressure guns, like a 357 mag or 44 mag.

Many of us in building seem to adhere to a minimum barrel wall thickness of .100" under our lug and sight feet as being the thinnest safe minimum (with 12L14 steel). It seems top pressure in most ML'ers goes up to about 20,000 psi. I think a 357 mag is around 30,000--and yes, I know there is a brass case to take up and distribute some of the pressure

 

[cal.45]

Have you done some measurements to see how thin the cylinder walls actually are? It would seem to be particularly thin under the locking lug detents. Might as well measure both old style BP guns, and modern high pressure guns, like a 357 mag or 44 mag.

Many of us in building seem to adhere to a minimum barrel wall thickness of .100" under our lug and sight feet as being the thinnest safe minimum (with 12L14 steel). It seems top pressure in most ML'ers goes up to about 20,000 psi. I think a 357 mag is around 30,000--and yes, I know there is a brass case to take up and distribute some of the pressure

The thickness of the chambers seem to be approximately 0.019” at the thinnest spots. Which is very thin..

A muzzleloaded pistol or cap and ball revolver have much lower chamber pressure than modern smokeless guns, like .357 mag. But if you look at a modern revolver cylinder, the walls are still pretty thin.

According to this site https://www.azom.com/article.aspx?ArticleID=6604 12L14 steel is weaker than the steel properties of my example.

 

[tenngun]

I don’t know, I look at test to blow a gun with god-awful charges. Sam Falada did a bunch. He couldn’t get a barrel to blow until he obstructed the barrel.

 

[Pete G]

Modern revolvers use heat treated steel; b/p guns do not.