Measuring a slug

[Nora]

Even numbers are easy. But how about an odd number of lands and groves. What is the best way to measure them. The example I'm looking for is 5. Thanks in advance.

Nora

[wallenba]

Been thinking on that one myself. I can't come up with a reliable method that the average guy can do with his own tools. I would try contacting a gunsmith or Brownells to see if they might have a "Go-No Go" gauge that the manufacturer would use, probably cost prohibitive. If you are trying to determine a best sizing die size, it might be cheaper but more time consuming to bracket with all sizes and experiment for best size.

[2Tite]

As usual, slug the bore with a lead slug. Then wrap the slug with a horseshoe shaped layer of shim stock. Measure across the stock and slug with a micrometer and subtract the thickness of the two layers of shim stock. There you have it................

[Jumping Frog]

I asked this question over on the S&W forum when I was sluggging a S&W 629 barrel.

Accurately measuring requires a special tool which I did not have and do not want to buy.

One suggestion was to measure the thickness of a strip of metal cut from a soda pop can. It was suggested that the thickness was usually 0.004". Wrap the strip of metal around the boolitand measure the boolit/soda can strip together. Subtract 2X the thickness of the soda pop can strip; it the thickness was 0.004", then you would subtract 0.008"

YMMV, internet advice worth what you paid for it.

[462]

Another way is to slowly rotate the slug within the micrometer's jaws, feeling for the resistance of the groove. Don't apply a lot or force to the jaws as you may distort the slug -- light pressure is all that is needed.

[briang]

If the grooves are small enough that you can get a bore measurement and a bore + one groove measurement you can subtract the one groove form the bore, then double the result and add it back it the bore and you should get the groove size.