How to Measure a 5-Groove Barrel
- 1). Unload the rifle.
- 2). Clean the bore of the rifle. Use a patch to lightly oil the bore.
- 3). Set the butt of the rifle on the floor. Set an egg sinker on the muzzle of the rifle. The correct size sinker will be too large to push into the bore by thumb pressure alone.
- 4). Use the leather mallet to drive the sinker into the barrel. Drive the sinker through the barrel and out the chamber end with the cleaning rod.
- 5). Set the sinker into the micrometer so two groove impressions (larger-diameter sections) of the sinker contact the V-anvil. Close the micrometer so its spindle contacts a third groove impression.
- 6). Read the indicated diameter on the micrometer scale.
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