Hello. 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 steel was inferior, so it got me to wounder about the steels of today. What’s the minimum (with a safety factor) thickness of a chamber (or overall barrel for a pepperbox or derringer) 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?
The old 1975 Lyman Black Powder Handbook lists the following data for a patched 92-grain lead ball - 2690 LUP (Lead Units of Pressure) with 25 grains of Gearhart-Owen FFFg, and 3760 LUP with 30 grains of G-O FFFg. LUP is not equal to PSI, but it should be in the ballpark. I would note that the 1975 G-O powder was produced at the Moosic, PA plant, which was shut down twenty-some years ago. The 1975 G-O powder was apparently comparable to the Swiss or Old Eynsford powders which are available nowadays.
