I have go to loads. A 250 grain 45 XTP in a Harvester crush rib sabot, 70 he of 3f Swiss lit with a Remington #11. 1575 fps from my 26 inch 50 XR and 1540 from my 22 inch ThunderHawk.
My bear load, a 300 gr ( non magnum) XTP and 90 of 3f Swiss, same sabot and cap, gets 1600 fps from the XR. Havent worked up the courage to try it in the ThunderHawk yet. Little thing only weighs as much as a high quality 22!
With Swiss, I find if I get shot to shot variations in velocity over 10 fps, I'm doing something wrong. Never could get smokeless to shoot that way.
This powder is just spectacular in my 45.
The .50 caliber loads seem modest by some standards, but the 250 grain load has removed the will to live from 9 deer at ranges from 12 feet to 150 yards.
Good fortune to you