Hand loading .6mm ARC

[Rickhem]

Does brass length matter? It depends on how precise you want to reload, but more importantly in relaying information. I stated that these are the measurements in my chamber and you should use a comparator and gauge.
Why brass length matters is, when using a OAL gauge your datums are actually the shoulder and the ogive but are measured from the base to ogive ( preferably ) or to the tip ( COAL ). If you take that measurement with two different lengths of brass when measured from base to shoulder you will get two different measurements.
I know it's common to share load data in COAL but I'm not a fan of it, it's imprecise information. That's why I gave MY info in MY chamber as precisely measured as I could given in a COAL measurement and of course there are always .002+- differences.
I hope my answer wasn't to confusing.

Maybe I'm mixing up some terminology, but when measuring COAL, or OAL, you are measuring the length of the cartridge, both brass and seated bullet.  Even using a comparator, you are measuring the cartridge base to ogive distance, which I agree, is a much more meaningful piece of data.  In any of those, the length of the brass is not impacting the final reading, since the bullet is inside of the brass.  The bullet, in effect, telescopes inside the brass, and the depth of that seating determins the COAL, not the length of the brass.

Now if we are talking about headspace, which is the measurement of the cartridge base to that datum line on the shoulder of that specific case, then that most surely matters, but that does not include a bullet in that measurement.  That measurement is also used in conjunction with the measurement of the chamber, which we get from a piece of brass fired in that chamber.  (actually an average of several pieces, but I digress)  What is interesting is that if you look up the SAAMI specifications for some cartridges, and look at the drawings for both the cartridge dimensions, and the chamber dimensions, there is occasionally an overlap.  The tolerance for a cartridge at it's longest "in spec" measurement, is longer than a chamber at it's shortest "in spec" measurement by a thousandth or two.  You'd think that couldn't happen, but it occasionally does.  

I think we're probably saying similar things differently, and I also think that giving a COAL without saying what chamber one has, or some other details, is not of much value.  A .223 service rifle frequently has a Wylde chamber, so sharing that COAL helps, but if one barrel has 3500 rounds on it, and another is new, that COAL has less value.  We definitely agree on that.  Every chamber is different.

Anyway, all this in the best intentions and in the spirit of good discussion.  I learn a lot from these kinds of threads between posters that forgot more than I know, so maybe we're helping someone just reading about the 6ARC, or loading for one.