I measured a box of 20 empty .270 cases (Winchester brand) and they measured on my digital caliper from 2.530 inches to 2.540 inches with the majority being around 2.533 inches.

Im looking to create as accurate a deer/antelope hunting load as I can. How anal do I need to be on having all the cases be exactly the same lenght? What is a recommended case lenght before loading? Mike

max is 2.540,with recommend trim to length is 2.530, IIRC

Case length is not all that important.
They need to be a couple thousands shorter than max length in order for the cases to stretch. and not go over the throat of the cartrage, if it does it can create high pressure.
Trim all casees to the same trim length.
Afrer resizing the case necks will stretch if you use standard dies. at that time you can trim to length.