Star,
That is how I load my 12 ga for cowboy action. I have had both shoulder joints replaced, so I lightened up my loads so I can shoot from the shoulder vs. the hip. These days I'm shooting smokeless, but I'm sure that with a little bit of trial and error, a good BP load could be achieved. Even when I didn't know my shoulders were so bad, my BP loads never went much above 40 gr of black. I've found when you go way up in grains in BP, you tend to waste powder.
Buckeye Pete