I recall reading an article many years ago by a gentleman who had a collection of "St Louis" double percussion shotguns. Several were by EC Meacham (SP?) as I recall. He showed a picture of the standing side by side & it was quite obvious in the pic none of the muzzles were square but slanted just a bit. He believe they had been built as Ball guns & this method was used for regulation.

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