How to Decap Brass

Decapping is the process of removing spent primers from brass cartridge casings. The primer is a small metal cup that contains an impact-sensitive explosive charge. When it's struck by a firearm's firing pin, the charge detonates, igniting the propellant in the cartridge. Ammunition reloaders decap brass cases with a decapping/resizing die mounted on a reloading press. The die uses mechanical force to press out the spent primer, while simultaneously resizing the cartridge back to within factory tolerances.

Things You'll Need

  • Reloading press
  • Cartridge-specific decapping/resizing die
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Instructions

  1. Preparation

    • 1

      Pull the operating handle of your reloading press to raise the reloading ram to the top of its stroke. Some reloading presses allow the handle to "overcam" to apply maximum mechanical force. If your press has this feature, do not overcam the operating handle. Raise the ram only until it reaches the top of its stroke.

    • 2

      Screw the decapping/resizing die for your cartridge into the frame of the reloading press. Turn the die clockwise until it contacts the shell holder on top of the ram. Turn the locking ring on the die clockwise to secure the assembly in place.

    • 3

      Check the setting of the decapping stem, which protrudes from the bottom of the decapping die. It should extend 1/8 inch below the top of the shell holder. Adjust the depth of the decapping stem by turning the knurled adjustment knob on top of the die. Turn it clockwise to lower the stem; turn it counterclockwise to raise the stem.

    • 4

      Push the operating handle up to lower the ram.

    Decapping

    • 5

      Insert a cleaned and lubricated cartridge into the shell holder on top of the reloading ram.

    • 6

      Pull the operating handle to raise the ram to the top of its stroke. To ensure proper full-length resizing of the cartridge, make sure the shell holder contacts the bottom of the die. Note that as the ram reaches the top of its stroke, the decapping pin will push out the spent primer.

    • 7

      Lower the reloading ram, and remove the cartridge.