Forget the oven method completely. Anyone doing it in an oven doesn't understand what they're trying to accomplish and/or doesn't know what they're doing.
6mmbr wrote:Brass which has been "work hardened" (sometimes referred to as "cold worked") is unaffected by temperatures (Fahrenheit) up to 482 degrees (F) regardless of the time it is left at this temperature. At about 495 degrees (F) some changes in grain structure begins to occur...
The critical time and temperature at which the grain structure reforms into something suitable for case necks is 662 degrees (F) for some 15 minutes. A higher temperature, say from 750 to 800 degrees, will do the same job in a few seconds. If brass is allowed to reach temperatures higher than this (regardless of the time), it will be made irretrievably and irrevocably too soft.
Heating the brass and not exceeding the change temperature does nothing. As the article states, change begin around 495 and the rate of change depends on how much you exceed this temperature by.
If you barely went over, by so little that the case head was still in usable condition you wouldn't have done anything worthwhile for the necks. If you anneal enough to make the necks springy you've ruined the rest of the case.
If you've slightly over annealed a neck 'work' will harden it up again, that is firing and sizing. It's not possible to recover from all over-annealing though. If it's been significantly overdone at just the neck it will be too soft to use and can't be rescued.