TexasCHLforum.com

Get some soft lead--round ball is usually pure lead--larger than bore and push through to slug the barrel. Measure the depths of the grooves (larger diameter) and my best luck with .30 cal bullets is to size .001 or .0015 over to cut out leading competely.

If you are using the lee push through sizer, you can increase the bore easily without machine tools. Take a cast bullet that is oversize for your sizer and put valve grinding compound on the side and little on nose of the bullet and push them through as if you are sizing. Do this a couple of times, clean (depends on whether you use water or oil based VGC, use water or solvent) and size a bullet and measure.

I encourage you to measure slugs with a micrometer, not a caliper. It is easy to get false readings with a caliper with lead slugs. If you do not have a mic, perhaps you have a friend, neighbor or mentor who can loan you one. You can pick up a fairly inexpensive mic at ENCO or even sears. Would loan one if you were close to me. I also have a special molt that is step tapered to cast slugs for checking barrel measurements.