Carpmaster I have one in 45 caliber also and Like Lanes mine likes 80 graines of Black Mag 3 with the 225 grain powerbelts. I shot mine for the first time the other day and got one inch groups with this load at 100 yds.
As the other guys recommended try the other bullets as well. I have always had good results with power belts in both my Knight rifles so I stick with them.

WV Mountaineer