I have a T/C Black Mountain Magnum but in .50 caliber. Mine has a 1-28 twist I was told. I also have mine scoped.

I found that 90 grains of 2f black powder and a Hornady 385 grain conical is very accurate. Also mine does shoot a number of different sabot combinations. But when I try to increase the powder charge... after all it is a magnum, well the accuracy really disappears.