How to Case Harden Gun Parts

Older firearms used case hardening to prevent the mild steel of the receiver and internal parts from oxidizing and rusting. The process involves applying a layer of carbon to the exterior surface of the mild steel, which has low tensile strength but is cheap and easy to form. The carbon forms a barrier against the harmful effects of oxidation and creates a colorful patina on the surface. Several companies provide kits for the home gunsmith to case harden their own gun parts.

Things You'll Need

  • Birchwood Casey Cleaner-Degreaser
  • Birchwood Casey Blue & Rust Remover
  • Brownells Color Case Hardening Kit
  • Braces and blocks
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Instructions

    • 1

      Strip the firearm down to the metal parts you wish to case harden. Clean and remove any existing finish and rust using the Birchwood Casey Cleaner-Degreaser and Blue & Rust Remover.

    • 2

      Brace and block the receiver to prevent warping from the high temperatures involved in case hardening.

    • 3

      Mix the charcoal compound. Using the plastic bucket provided in the kit, mix the wood charcoal and bone with a four to one ratio. Blend the two together thoroughly to prevent clumps.

    • 4

      Pack the canister in the kit with the charcoal mixture and gun parts. Ensure that none of the parts touch each other or the sides of the canister. Keep a minimum of one inch of charcoal over the top of the parts in the event of settling. Leave no airspace at the top of the canister.

    • 5

      Heat the oven to its highest temperature. When the oven reaches 1400 degrees Fahrenheit, place the canister inside using the tongs provided in the kit. The temperature of the oven drops when the door opens. Allow the heat to return to 1400 degrees then adjust the temperature control to maintain it. Heat the canister for 1 to 1.5 hours.

    • 6

      Quench the parts. Fill the quench tank with water between 45 degrees and 100 degrees Fahrenheit. Using the tongs, remove the canister from the oven, remove the lid and dump the contents into the quench tank to cool them.

    • 7

      Temper or protect the parts. Critical parts need tempering to prevent brittleness. Heat a standard kitchen oven to 350 degrees Fahrenheit. Heat the parts for one hour and remove. Coat any other parts with gun oil to prevent oxidation.