Lee 7mm Backcountry Factory Crimp Die. 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. Specifications for Lee 7mm Backcountry Factory Crimp Rifle Die: Manufacturer: Lee Caliber: 7mm Backcountry Projectile Caliber: .284 Caliber Package Contents: Lee 7mm Backcountry Factory Crimp Rifle Die Lee 92279: 7mm Backcountry Factory Crimp Die