The use of case gauges will indicate whether your resized cases are within SAAMI tolerances but can result in oversizing cases for your particular chamber. There are several tools available for measuring fired brass and can be used to set up your dies to your particular rifle. The Hornady, RCBS Precision Mic and Innovative Technologies tools all work well. For my bolt guns, I prefer the IT gauge since it is very accurate but does not work well for gas guns. The RCBS tool work better in that situation. I typically neck size but on occasion have to bump the shoulders with a body die. I set the die to set the shoulder back .0015 to .002. This allows easy chambering and doesn't overwork the brass. The process of setting up FL is the same as with body dies.
One way to determine bushing size is to measure the neck wall thickness multiply by two then add the diameter of the bullet. Then subtract the desired neck tension. Example for 22-250: brass has a neck thickness of .014 x 2 = .028 + .224 =.252 - .002 (desired neck tension) = .250 bushing.
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