Lyman's MSR Die Sets are engineered specifically for MSR ammo and are a must for anyone reloading for a modern sporting rifle. The sets include a Small Base Sizing Die designed for semi-auto use which will size cases to a slightly smaller diameter to ensure smooth chambering. Each die set comes with a separate Seating Die and Taper Crimp Die. The Taper Crimp Die is designed to give you added bullet grip for functioning through semi-auto actions. Lyman's MSR Die Set also includes an Ammo Checker gauge, machined to minimum chamber specs. If it fits, it will chamber. These dies have a black oxide finish and are packed in a foam lined storage case. This item is for 308 Winchester.