Lefever H 12 Gauge Questions

[Bruce Day]

The Lefever catalog contains much information concerning the guns and loading, and is available from Dr Bob Decker.

See below for cartridge length.

[Drew Hause]

Carman Fluid Steel (no idea what that was) offered in 1908
https://books.google.com/books?id=5U...&pg=PA1139&lpg

1912
https://books.google.com/books?id=Uy...g=RA4-PA73&lpg

“Maximal Average (Service) Pressure” for 850 BAR shells is about 10,700 PSI. The Ely loads are probably less (but Ely is unlikely to tell you ) but the RSTs are about 6000 psi.
As Frank suggested, I would not use the gun with any load until the barrels have been evaluated by someone with the expertise, equipment, and interest to do so.