Powder coating, my H&R 38-55 has a bore of .383, great quality control. The biggest stock mold I could find was a NOE @ .381, tried paper patching to bump up the dia that worked but was labor intensive. Tried powder coating, one coating and the dia was a little over .382 , 2nd coating came out to .383+. I run those thru a .383 sizer and now II have a very accurate bullet, Just in time for Ohio gun season.