Measuring barrel slug in barrel with odd number of grooves

[Jackpine]

Hello the fire,

I recently read a post regarding a barrel with a odd number of grooves and problem with measuring when slugging the barrel, and that it takes very expensive equipment to accomplish this task. When I first ran into this problem many years ago, used what I thought was a simple solution, which seems to work, but I have never seen it recommended anywhere, so maybe there is a flaw in my method.

My method is to take a narrow strip of shim material, no more than .003 thick. I wrap it around the bullet snugly, pinching the "tails" of the shim material between my finger and thumb to keep it tight around the bullet and measure the diameter, including the shim material. I then carefully measure two thicknesses of shim material and subtract that measurement from the wrapped slug diameter, and have my number. Takes seconds.

Am I missing something here?

Jackpine

[pietro]

.

Nope, as long as the micrometer/caliper is accurate.

.