My 12 SXS smooth with 24" tubes (early 1900's rifle with "Fluid Steel" bls), failed in the wrist on the second shot with round ball and BP. I re-bed the action and was able to use a crosspin (screw) as well to hold it together. After that, if held for another 20 shots or so with the 7 drams of 2f and an almost 500gr. round ball.
I then switched to smokeless which kicked about 1/3rd as much as the BP load had.