I have a .45/.410 Bond Arms Snake Slayer Derringer. For close up self defense it's hard to beat, but for any distance beyond 10' it's shoot and pray.
It has a 3.5" barrel with only 1/2" of rifling, so when firing .45 Colt rounds they have to jump about an inch + before they engage the rifling. This causes The boolit to tumble.
Would the hollow base of a Minie ball (cast from soft lead maybe?) expand enough to keep the Boolit centered in the chamber until it engages the rifling? Hopefully improving accuracy.
I have no idea what issues a Minie ball seated in a .45 Colt case will bring up. Just a stray thought rattling around my head.
P.S. I'm thinking of using Lee Improved Minie ball mold.