The RCBS AmmoMaster .50 BMG Shell Holder is just what you need to hold your .50 Browning Machine Gun (BMG) cartridge cases in place for reloading. This shell holder is designed to be used with the RCBS AmmoMaster, fitted to the top of the press, where you would normally find a die on a standard reloading press. Simply slide your .50 BMG cartridge case into the RCBS AmmoMaster .50 BMG Shell Holder at the top of your press, then fit the press ram with your primer holder. When you move the ram upward, the primer will be inserted into the case