I am using the Lee mold .379-250, which I have lapped out to cast a 0.3805" bullet. The bore of my H & R Target rifle slugs out to 0.3805". I am hoping to find an alloy that will bump up upon firing to work in this rifle. The alloy which I intend to try is 96% lead, 1.1% Tin, and 2.9% Antimony. Does everyone think this alloy will do what I need? I have been shooting it with 17.2 grains of IMR 4227. BTW, I do not own a sizer.