Pete,
If I did the shooting it'd be as bad as you thought! LOL!
These blokes take it rather seriously, and wear a shooting jacket, like a straight jacket I think...never had one myself.
Bob,
If the powder charge was up these, a barrel as you describe would work I think.
When I used the musket with 120-odd grains of 2F, (what I had) the.750 " ball expanded and filled the bore that measures .760", so if your theoretical barrel was 'choked ' all the way to the rifling, the patch would have to stay put.
I was using a thick wad below the ball and a thinner on top when I noted recovered balls had an 'equator' or flat section around their girth.
Richard.