CBTO will remain consistent but you will have different neck tensions. Will matter if you’re at the bottom edge or top end of charge range. Get a Little Crow Gunworks trimmer for the brass you use most and a manual for the rest. As much 308 as I shoot I couldn’t imagine doing them manually.
Actually variance in neck tension can and does cause variances in seating depth or CBTO. Another thing that can throw you off is if the primer pockets are not uniform you can get a misreading CBTO by having a primer sticking out a thou or 2.
