As other here have said for "hot" loads you want a slow powder! Fast powders can spike in pressure really quick with slight changes in charge weight, oal, etc. 800x although not fun to work with (needs hand weighed ) will give top velocities in all service calibers. Although I AM NOT RECOMMENDING this power level!!!!! In a purpose built 6.6" 17L barrel I achieved 829 ft lbs with a 130 cast bullet of my design using 800x powder. This was a long throat barrel with a muzzle brake . Longshot, Power Pistol, 800X , HS6 etc. Is what you want for hot loads.