RE: 54 caliber powerbelts???
I am shooting Hornady 300gXTP MAGwith a split rib sabot out of a Hawken Flintlock, 1-48 twist and they shoot just fine with 100g of Goex. I sight them in at 13 yards, then go out to 50 and get it grouping there about 1" high, this is dead on at 75yards.
Chap