The RCBS Ram Priming Unit for the 50 BMG is a great priming tool for reloaders who want to prime on the upstroke for maximum sensitivity. The unit works by holding the cartridge case in a shellholder on the top of the press (where the die is typically installed) The press ram is then fitted with a special primer holder (plug assembly). By moving the press ram up, the primer is inserted into the case. Notes: Includes flat and cupped primer plugs