Another case length question

[Riverguide]

I have two different guns I am developing loads for.

The first is a 300/221 on a CZ-527 platform that i bought second hand and do not know who made the barrel. It chambers 1.40 case length cartridges just fine. This is all brass that came from Hoser originally and has now been fire formed in this gun. I am checking the case length on this batch of 50 and they are anywhere from 1.365 to 1.340

My new SSK 300 Whisper came with 300 pieces of JD's 300 Whisper brass and they all measure 1.355 (new, unfired).

So my question is this. How important is case length to accuracy? Should I be more concerned about bullet seating depth (COAL) instead of trimming all the cases to the same lenth?

Since 1.34 works in the 300/221, I am thinking about getting more brass from Hoser or Lou44a at this lenth. Then I will trim anything <1.34 down to 1.355 for my 300 Whisper.


Riverguide

[Hoser]

Your first firing of brass can cause it to actually shrink as the case is fireformed to the chamber.

If you are shooting a benchrest match, then yes case length and neck tension matter. It may mean the difference between a 0.010 group and a 0.125 group.

Too short, not a big deal. Too long, it can be a big deal.