Dan,
Even the AMP (Annealing Made Perfect) electric annealing machine, can overdo it. When I tested one, they had a list of cartridges/manufacturers with the digital settings. I had some .30-06 cases from a manufacturer they listed, and it over-annealed those, which required a couple firings before they returned to normal. The problem is 2-fold, because even brass from specific manufacturers varies from lot-to-lot; and quite a few major manufacturers make brass for each other. This may seem odd, but it happens far more often than many handloaders suspect.
It was no big deal, but even with the AMP (which retails for over $1000) there can be some tweaking involved in specific brass.
