Generally speaking, for rifles maybe-depending on your bullet and load. For most handgun loads, probably not--but for best results with either, use a bullet with a plain-base design if you're not going to use a gascheck. If your next question is going to be about bevel-bases, I myself buy those if I find them at a really bargain-price, and use them for handgun-plinkers, or melt them down with the rest of my alloy to use with plain-base or gascheck molds.