Thread: Seating depth

Originally Posted by ebf

Er, the Hornady AOL gauge (comes in straight for bolt or bent for semi variants) is used together with the modified case to determine where the lands are for a particular projectile...

The "barrel" thing you talk about uses either a bullet comparator to give you a CBTO measurement, or a headspace comparator to measure case base to shoulder datum.

Case length (unless it is REALLY wrong) should not affect ogive measurements.

14 thou difference in CBTO is not slight, that is a big variation.

Take the hornady bits off your caliper, measure the case lengths...

Put the bullet comparator on, and measure your projectiles, from the base of the projectile to the ogive...

One of those should tell you where the variation is.

Take 3 projectiles, use the AOL gauge and modified case and get an average of where your lands are, subtract 0.010 from that and use it as the starting seating depth.

Sorry for the typo on the AOL gauge ebf, I see you picked that up. Slightly anal, you knew what I meant.
I do everything you have suggested anyway. My question mainly was if the cases are all different sizes will that make any difference to the ogive measurement when I use the comparator on the caliper to measure from the base of the case to the ogive?
Because my cases are all different sizes. My trimmer only trims to one size, I don't have a trimmer that is adjustable yet, it is on it's way though.