Ok I've seen this mentioned left right center and really need to know exactly what is involved to a) do this and b) ensure that i get the right measurements to be able to use the information.
I ASSUME that the purpose being to measure the diameter of the barrel you have to use a soft something or other which will mould to the rifling much as a bullet does?
I ASSUME that one needs a micrometer to measure the OD of the item which has been pushed through the bore, and thats about as far as I get.

What do you use? What do you push it though with? Do you have to oil it? Do you measure the bit that has been in the groove or on the lands etc etc? plus of course once you've done this what is the formula for max accuracy in reloading. if one gets a dia of .310 does one use .311 bullets for instance.
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