Lyman Auto Neck Expanding M-Inchdie (40 SandW/10Mm) Improves accuracy of cast and jacketed bullet reloads The first step expands the inside of the case neck to just under the bullet diameter for precise case neck tension in the finished reload The second step expands the case mouth to bullet diameter or slightly over Allows the jacketed or cast bullet to be started perfectly centered in the case mouth and properly aligned with the axis of the case neck Can be adjusted slightly deeper for a slight flare for seating cast bullets