You really can't go wrong with a GM 58 caliber. I shoot 90gr of 3f GOEX behind .570 PRB lubed with bear grease for my hunting load. I prime with Swiss Null-B. It is accurate and very hard hitting. With that load I have always gotton a complete passthrough on every deer or hog that I have shot. Please keep us posted on your new barrel and the development of your favorite load.