Minnie in smoothbore

[CoyoteJoe]

Sorry for the confusion, I was just replying to the post, not specifically to you.
What I was attempting to get at was that I should think a much larger and deeper cavity, more like a modern shotgun slug just might keep the minie going nose first from a smoothbore. The cross section of a shotgun slug looks like an upside down "U" with the nose a little thicker than the sides. The lube grooves on a minie would probably prevent making the cavity that large but I suspect a larger cavity would still be better.

 

[nkbj]

The shuttlecock shape that's needed for no spin is a toughy to muzzleload. How would you keep it straight without a discarding sabot?
Would the shape be somehow adaptable to a pressure expanding skirt?

 

[CoyoteJoe]

Both Lyman and Lee produce molds for hollow based slugs which are designed to be loaded inside the common plastic shotcups. How well they work I have no idea, but of course they aren't made in .54 caliber. For anything to shoot accurately it will have to fit the bore, either with or without a shotcup. I have a modern 12 gauge pump smoothbore with open sights on the barrel which has produced 6" groups for five shots at 100 yards, but it does that with only one of the many comercial slug loads I have tried, that load uses wads attached to the base of the slug and the lead slug itself is a tight fit in the bore.