How to Knurl a Bullet File

Knurling is the process of inlaying a diamond-shape, or intricate crisscross pattern, on an object. A bullet is typically knurled in order to make for a snug fit inside a smooth bore rifle, such as with muzzle-loading weapons. Knurling is easily accomplished using a coarse cut mill-bastard file. After knurling the bullet, the outer diameter is slightly raised, which helps the bullet seat fully into the bore like a sabot. The resulting tight fit allows the powder to expand and propel the bullet without the use of paper patching.

Things You'll Need

  • Padded gun vise
  • Workbench
  • Mill bastard file
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Instructions

    • 1

      Unload your weapon completely. Visually inspect the weapon to ensure that no live ammunition is present.

    • 2

      Secure the weapon in a padded gun vise. Ensure that the muzzle is accessible.

    • 3

      Fit the bullet into the muzzle. A non-knurled bullet will easily slide into the barrel with little finger pressure.

    • 4

      Lay the bullet on its side on a flat, hard surface such as a workbench. Set the file flat on top of the bullet.

    • 5

      Push down on the file with the palm of your had using firm pressure. Roll the bullet back and forth. Fit the bullet into the muzzle again. It should not be able to be pushed into the bore using finger pressure. Tap on the bullet head with a rubber mallet. The bullet will sink into the bore. This is the type of fit you're looking for.