Resized case length vs fired length

[PA_Allen]

Yes .020" is a lot. I use gage "B" for the Grendel and measure .001 to .005" difference between resized and fired cases depending on the brass and load. Use your headspace gage to set the once fired shoulders back 0.003 to 0.005" and you are good to go. Note that your die setting may be different for different brands of brass. I have to set my die slightly different between the Hornady and Lapua brass to get 0.003" setback for both.
Best
- PA