Measuring lands in Tikka 22-250

[Diddums]

I assume when you mean your chambers coal you mean the measurement to the ogive when the bullet is touching the lands...?
Keep in mind this measurement will be different for every type & even often each different batch of bullets.
yes, I measured it with a bullet comparator kit. I did measure about 10 projectiles from the ogive and there was a bit of variation by a couple of thou.

Im not sure what others do, but i only bump the shoulder back enough so it chambers without resistance-or ideally when i can just feel it as per marksman's suggestion when finding the lands (feeling for same but with shoulder of case, not projectile)--so .001"-.0015" shorter is plenty...i think .004" is too much bump--your just working the brass unnecessarily & risking different results from load testing due to smaller case capacity with such a large bump.

Just check cases in the chamber as you wind the die down & lock the die when the cases are just chambering ok as per above--i like to try a few cases each time you change the die just to be sure.

Headspace/case shoulder measurement variations--do you mean variations from sizing a case, or measuring a once fired case...?
I mean that when I'm sizing the cases they were all coming out of the press exactly the same length, there was a bit of variation.

Either way i easily get variations of .001" & believe its ok.
however id suggest only neck sizing once they are formed to the chamber.
Once formed to the chamber i still sometimes get variances of .001", but i have sometimes found new cases take a couple of firings to fully form. (Or more to the point they probably spring back less after a couple of firings).

I think 5-6mm of the bullet seated in the case is fine mate-thats basically calibre depth, & ive seated them less than that.
I wasnt sure as they are a lot longer than the max cartridge length in a reloading book

That is a cracker of a casualty...ive had the odd dent in the shoulder from too much lube build up, & a split neck from lack of lube, but that ones a wee ripper...id frame it & give it pride of place on the top shelf of the loading bench...!!!
I pushed on the press a little too much and that was the end result.

[sungazer]

Yes that is am issue with Hornady seating dies. a lot of seating dies you can adjust so the shell holder touches the die but not one of these. You have the seating die wound down to far it needs to be wound out a few turns. It is also a die that will put a crimp on if in too far which you dont really want either. I assume you re read the instructions and worked it out?

[Stix]

Not sure if this will help diddums...
But one thing i do for consistant measuring, when fitting the hornady measuring equipment to calipers...

I leave the grub screws loose until everything is pushed up together/calipers are closed.
With thumb pressure still on closed calipers i then do up the grub screws & zero. It just helps to ensure no movement can happen.

You get to know certain measurements for certain rifles & bullet batches in your head & soon know if the comparitor bits aren't in the right spot on the calipers.