Negative Headspace Measurement(s)

[BadMatrix]

I am using the RCBS Precision Mic to measure headspace

I measured the headspace on six fireformed .223 and got the average headspace of minus 0.004, which is less than the SAAMI MINIMUM FOR .223 (Ruger American Predator .223) Now What?

how do i bump this 0.002 ?

 

[Mobuck]

When I loaded only for bolt action rifles, I adjusted my dies to create a very modest "crush fit' condition with the reloaded ammo. This resulted in some very accurate ammo and the occasional fail to chamber if even a shadow fell upon the open chamber.
Then I began reloading for semi-auto rifles in great volume and every case was sized to fit the tightest chamber on the rack. Guess what? The overall accuracy didn't deteriorate nearly like what I'd been warned it would AND after loading 10-20K cases, I've not had a single case separation so far.