Re: Neck turning for a factory rifle?
Are you using a die with a guideing sleeve, like the Redding Comp die?
I neck turn for 100% clean up, no more than necessary though. I don't leave a thin spot anywhere, however small. Inconsistant neck tension for one, and stretching in the same weak spot every firing may lead to a real thin spot that split more readily.
It's my opinion that a factory neck is way too loose to begin with and work hardening is far too rapid to ever keep consistant neck tension without bushing dies and something to measure seating force.
How many guys are out there that set a barrel back a half inch or so in order to get a tight neck and maybe a shorter throat in their factory barrels?