round ball are smaller you should start with 40gr. and go up till you get what you want. grouping or killing power. being able to go though 3to 4 in of card board or 1to 2 in. wood will kill. try all different lubes I like bore butter but that is me.I am very knew to this and had read that 60 to 80 grains was typical. Not sure how your 350gr bullet compares to a patched round ball . I assume this is a conical bullet. I am hoping my biggest problem is that my store bought lubed patches are too dry. I ordered unlubed patches to try again.