How to Measure the Bore of a Barrel

Over the course of standard usage, a gun's barrel deteriorates from pitting and mild erosion. Sufficient damage can render the barrel unusable and ineffective. Measuring the bore of the barrel is the best way to keep track of the ongoing changes in the interior of the barrel and provide data to track the alterations in the size and shape of the bore.

Things You'll Need

  • Bore gauge
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Instructions

    • 1

      Clean the barrel completely, making sure all residue and remnants that can affect the measurement are removed.

    • 2

      Allow the barrel to cool to room temperature after using it. Do not measure a barrel that is still hot from use, because heat can change the shape and size of the bore.

    • 3

      Fix the proper attachment for the barrel's caliber to the plunger of the bore gauge.

    • 4

      Insert the plunger carefully into the end of the barrel. Do not force the equipment into place, and do not apply any lubrication to allow the piece smoother movement. The plunger should fit easily into the barrel.

    • 5

      Extend the plunger until it reaches the length of the barrel, but do not extend it past the feedport, which will mischaracterize the readings.

    • 6

      Take a reading at the first point from the gauge dial, then retract the plunger an interval and take another reading, continuing until you have reached the end of the barrel.

    • 7

      Take as many readings as you wish, but generally 1-inch intervals are sufficient to give you a good sense of the condition of the barrel.