Looking at a Black powder proofed gun, 2 3/4” chambers, reproofed in 1980, trying to figure out what the service pressures should be? Or are all Black proof guns to be considered the same if 2 1/2” or 2 3/4” with service pressures in the 5,000 range? After 30 plus years I finally have a basic standard pressure load range for Nitro. Black powder pressures are the last piece of the puzzle. So what is the general answer.