Not extensive experience, but I have shot some of the Cast Performance Co. .454 Casull bullets using sabots (265-grain, .452" WFNGC)in my .54 Kodiak SXS double. The test was to see if the 1/66" twist in this rifle would stabilize them. It did, out to 50 yards, which is the longest range I tried them at.

The load I tried was 120 grans f Pyrodex RS, and the rifle shot OK. However, I did not try to "regulate" this bullet by trying different powder charges.

My "standard" load in this gun consists of the .535", 230-grainSpeer PRB with 85 grains of Swiss FFg. This load regulates at 100 yards as shown.....