Just starting out reloading. Starting on .223 got rem fired brass from midway. Using redding fl die on a rock chucker. My problem is when I'm sizing the cases according to redding (raise ram touch die to case holder) my headspace is to short on my Dillion case gauge. Do I just back it up a little then? Also it's appearing most of these cases oal is to short  according to the case gauge. This gauge is kinda hard to tell by feel or sight any tips on that? Bullets will be for an AR btw.

Thanks

Oal or trim length ?

Length of the case after sizing I haven't trimmed it yet and it's already to short according to the case gauge. I just took a caliper to some of them though and the shortest was 1.748 the rest were okay. Maybe my eyes are worse then I thought

Once fired? Because new brass shouldnt be that far off. Every now and then i get range brass that is off. But your COAL is what ultimately matters.

How do cases fired from your rifle gage?

Mixing shell holder brands and dies can cause tolerance stacking issues.

Most dies will size acceptably when adjusted as per instructions.

Some dies need to be adjusted down tight against the shell holder to work. Sometimes the shell holder needs to be modified to work.

It seems to me that you may be confusing headspace with case length. Case length in .223 is 1.760" maximum. Anything shorter will work fine. Trim to 1.750" whenever you reach the 1.760" maximum. All case lengths must be measured after resizing, never before.

I use Mo's (Mo DeFina) case gages and think they are the best. They are not cheap. Hornady's Lock-N-Load headspace gage is the best value for the money. It will allow you to accurately measure fired and resized cases to within .001" and adjust your dies accordingly. You can use calipers on simple drop gages provided the case mouth does not protrude (indicating a need to trim). Case mouth protrusion will interfere with the calipers and make it impossible to get an accurate reading.

I set my dies up to get -.001" to  -.002" clearance for bolt actions, -.003" minimum to -.005" maximum cleance in semi-autos. I find it impossible to hold headspace tighter than +/- .001" when resizing. I know that going into it and an OK with that.

The shell holder should measure .125" +/- .001" when measure with an RCBS vernier caliper. This will give the correct Full length sizing 99% of the time. If your FL sized brass will not let the bolt close, check to see that the die & shell holder are contacting each other AT THE TOP OF THE PRESS STROKE. If the are not touching, screw the die down/in more. Your trim length is ok.