You cannot expect a manufacturer to predict the expanded ID of the case mouths for your cases. Brand, thickness, number of firings and work hardening of the brass all contribute to sized ID of the cases. You need to figure out what a .310 or 0.311 diameter expander expands your cases to.
For a 0.311 diameter bullet I would use a 0.311 expander for target ammo. The brass should spring back 0.0005-0.001" from the sizer diameter. Again, depends on your brass. For hunting loads and/or tube magazines I'd use a 0.310" expander for 0.311 bullets
Again YOU need to find out what works for your brass.
A 0.308" expander may work for some people with hard boolits, but I shoot soft alloy and like my neck expander to be boolit diameter of slightly smaller.