270,
I'd be interested to know what is the diameter of your cylinders?
Take an diameter measurement of a couple sized cases. Fire them, and measure the diameter of the fired case.
The difference in that measurement is what is causing your OAL of your case to grow--not the carbide sizer "stretching" the case.
.010" still seems like of lot of case growth. I would venture that the diameter of your cylinders are on the up limit of spec.
