Thanks Parabola. I did shoot some 16ga high brass rio (largest rim I could find) reloaded to 6k with a roll crimp. They actually patterned well at 23yds. Gun is all original 12ga with one of the first breech loaded brass cartridges. Don’t know why they chose a 14ga size chamber with .726 bore but they did. I will have RMC make me 25 correct size brass or have the chamber and rim opened up to todays 12ga. These are really well made guns and barrels are Birmingham Black powder proofed. I know it sounds horrible but this thing would be great with some regular 12ga paper hulls loaded with pb and or 800x at 5500 psi. I’m sure Dean Harris at skeets could do it well.
Thickness at breech is .150 in and maintains .100 all the way 12” down past my hand with no real pits only slight frosting. It feels like 7.75lbs but I bet it 8.5.