The name helps tell the story. A form and trim die is used when making one cartridge case out of another. For example, making 30 Herrett cases out of 30-30 cases involves such a die. The 30-30 case is pushed into the die, forming the body, and the excess length now sticking out of the top of the die. A fine tooth hacksaw is used to trim the excess length. The top of the die is flat and specially hardened for wear resistance.
