Quote Originally Posted by bigedp51 View Post
The RCBS Precision Mic is designed for only one caliber and the Hornady cartridge case headspace gauge will fit any cartridge.
I prefer the Hornady gauge used with a digital vernier caliper with big numbers for old eyes.

Below a Colt 5.56 Field gauge at 1.4736



Below the same headspace gauge in a adjusted Hornady gauge at 1.4735



Below a "fired" Lake City 5.56 case from my AR15 that give me a idea what the actual headspace is minus brass spring back.
I then use this reading to adjust my full length die for .003 shoulder bump.



I prefer the Hornady gauge because you can spin the case with your fingers and get more accurate readings.

With the RCBS Precision Mic you can't spin the case to center it and you get variations in the readings.

Below my RCBS Precission Mic and you can only use it with the .308 and .243. You have to open and close the gauge several times to get the case to center and get the shortest reading.



Below a fired .308/7.62 case in a Dillon case gauge, this case is a once fired Lake City case and fired in a military chamber.



Below the same case in a JP Enterprise case gauge, and this gauge is closer to minimum SAAMI diameter.

Meaning if the resized case fits in the JP Enterprise gauge it will fit in any chamber. And the Dillon gauge is larger in diameter and only checks shoulder dimensions.

Bottom line, if you buy bulk once fired Lake City brass that was fired in larger diameter chambers the JP Enterprise gauge checks case diameter. After sizing you are dealing with brass spring back and range pickup brass or once fired military brass may not chamber in your rifle.

Excellent right up with illustration you have there , thanks for your time and input.I will probably go with the hornady gage to use on the bolt gun..as i only want to move the shoulder about .002 or so when i need to .I have a wilson oal gage in 223 that I use on the ar because of range brass and running 2 rifles.i just take them back to factory specs..1 ar is a varmit version with a whiteoak armory barrel when I get the gages in the hornady kit I might tinker with the case headspace in it.i like the way the hornady gage works didn't know about durability Or repeated use...thanks again