I have had the same problem with Winchester nickle cases in my .270 wsm. I had to adjust the die another 1/4 to 1/2 turn closer to the shell holder. There was quite a caming effect! I asume the nickle coating is not allowing the brass to fully resize without the extra force applied by turning the die down a bit extra.
Try adjusting the die bit by bit and testing the case in the rifle. If it doesn't fit, adjust some more, test, repeat until the case fits.
I finally quit reloading nickle cases and stick to staight brass, now.