Mark, Richard has given an excellent discription of how to use a pin gauge. A slight taper ground and polished on one end is required as well as a good lube.
I must confess that I use this set mostly to measure bore diameter since purchasing a 12ga hydraulic dent remover.By adding a brass shim under the anvil of a 12ga dent remover you can also do 10ga. It is a slow and somewhat tedious process useing plugs to remove a dent,but it's an operation that requires care/patience anyway. They also beat spending 100's of $ for a hydraulic unit if you only have one or two barrels to do.They can be found on ebay fairly cheap if you watch.Here's an example.
http://www.ebay.com/itm/M2-Minus-Plu...item5ae3bc2dc7
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"Double guns are a sport and a pastime built into a beautiful package to which I attach myself when entering the great theater of autumn, those days now grow more precious because we are given so few".. Robin Lacy
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