Lee 45/70 LEVERevolution Factory Crimp Die for crimping the shorter case length needed to load leverevolution projectiles in 45-70. lee factory crimp die crimps the bullet in place more firmly than any other tool. Tests demonstrate that even bullets which have no crimp groove will shoot more accurately. A firm crimp improves accuracy because pressure must build to a higher level before the bullet begins to move. This higher start pressure insures a more uniform pressure curve and less velocity variation.