[Unclenick]

Low pressure for sure.

Hardening doesn't change the brass's modulus of elasticity (a measure of how much force is needed to stretch a material). What it does change is how far you have to stretch the brass before you exceed its elastic range and it starts to deform (this increases with hardness), and how far you can stretch the material before it breaks (this decreases with hardness). So, measure your cases before and after firing. If annealing allows them to come out of the chamber bigger (yield point exceeded) than your hard cases do, then it is reducing the sealing pressure. But if the annealed cases come out of the chamber the same size as your work-hardened cases do, then it isn't making any difference.