Tigger,

I once had some old remanufactured 6.5 arisaka ammo that had been resized from surplus 30-06 ammo (how's that for irony!) The stuff kicked like a mule so I only fired off a few from the couple boxes I had and forgot about them for 7 or 8 years. When I looked at them again there were a lot of split necks, that I did not remember from before. However, to me they looked like work hardening type stresses rather than something chemical.

Sounds like it to me too. The ones I referenced were supposed to have sat around for much longer; 20-30 years.

Tigger,

These boxes were old when I got them, I have no idea how old but at the time I was guessing 15 years or so.