In hundreds of thousands of sizing cases, I have NEVER had a case(s), two (2) 270 caliber Winchester brass exclusively, that REFUSED to neck down in the sizing die.
After FULL LENGTH sizing (two blocked die to shell holder and overcam on Rockchucker) the 0.277" mic'd bullet DROPS INSIDE THE CASE with ease. No neck tension at all. I resized them again. Same result. Not doing it again or I will go insane expecting a different result.
I will mic the sizing button...stand by. Nope. 0.2745" (+/- 0.0005") sizing button.
Necks are mic'd at 0.2985" out to out - so that SHOULD be "squeezed" by the sizing die - WTH?
Cases are both trimmed, as all others, to 2.540". Neck of case above shoulder is fire formed at 0.60" on each.