Hodgdon only lists Titegroup with the 360 cast GC @ a start of 13.0 grains and a MAX of 15.6 with a max pressure of 55,700 PSI , and speeds from around 1200 to 1340 FPS . Their web site does not show the 300 XTP but you could call them and they may have some loads for the 300 gr .
stimpy