Let me share my experience. I was forming 256 Newton cases from 270 Remington and Winchester once fired brass. I was using Imperial Sizing die wax. This was a horror story, I was dealing with stuck cases and dents. Lube was coming out of the vent hole in the RCBS dies. Unvented, the C&H dies were sticking cases also I swapped over to the new style RCBS lube. Problem went away. My feelings/personal experience is that Imperial does not work well for reforming cases. This stuck case situation had mainly to do with lube type. This shortfall was evident also when the RCBS dies were used to form 45-60 from Starline 45-70 brass. Reforming worked great with the RCBS lube.

This is not bashing Imperial. I have used Imperial long before Redding bought them out. In my experience a wrong or inappropriate lube can bring on stuck cases. Most of my dies came to me used. Any break-in was done by former anonymous owners. The Newton dies were both new with the RCBS being NOS from a going out of business sale many years ago.