JonJ said:
Thanks Tony. But now I'm beginning to feel a bit over my head. I didn't realize that there are so many different gauges for so many different measurements. I'm searching google right now trying to figure out what does what!
Hah! It sounds more complicated than it really is.
You need measure three areas:
1) Case length from base to shoulder. Auto-loaders need to be slightly undersized to feed and chamber reliably. You find out what yours is by first measuring those 5 fired pieces I talked about. Then, it's simply used to set up your die down until it sizes the brass to the length you want. So far, I've had good luck "bumping" the shoulder back .002" from my fire formed measuement.
2) Overall case length after you size. Using just your calipers, measure the case length so you can set up your trimmer.
3) COAL (cartridge over-all length). From the base to the ogive in order to seat your bullet to the correct depth. Either mag length, or long for the 80's.
The gauges are very easy to use. They attach to your calipers with a thumb screw. Zero your calipers when it's closed. Attach the comparator body with the thumb screw and attach one of gauges with the set screw. Then, close the calipers on the gauges and measure how long they are and record that number. Insert a case, measure it and subtract, and you have you net length.
Example:
My fire formed brass measured 3.460". My comparator body and headspace gauge measured 2.003"
3.460 - 2.003 = 1.457" (length of case from base to shoulder. Then, I set up my sizing die and screwed it down until my brass was 1.455" (net) Viola! Perfectly sized brass for MY chamber.
The comparator works in the same way. For mag. length, I simply measured 5 pieces of factory ammo and set up my seater until they came out to that length. Then, I just usually check each 10th piece along the way to make sure it's still doing right.
Hope this helps. Let me know if you have any questions or confusions.
