If I were going to shoot a gun with bbls having an .018" wall thickness 9" from the breech, I would want a light shot charge propelled to a very modest velocity by the quickest burning powder I could find, thus giving the highest chamber pressure for "That Load". I would want that pressure curve falling as rapidly as possible as it leaves the chamber not being in any way maintained further down the bbl.
Personally I have no desire to shoot one that thin, that close to the breech.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra