Speer manuals #9 and later have tested data for .45 Auto Rim with 250-260-grain bullets. They top out at 6.2 grains of Unique with the 250 grain lead SWC for 824 fps. I would not be inclined to exceed that. In the .45 ACP with 260-grain JHP max. is 6.4 Unique for 822 fps.