Two different brands of brass were probably annealed differently, and are different metallurgy. If you didn't anneal them, wouldn't be at all surprised to see different springback. Try more dwell on them first, see what they do then. What kind of lube in the neck won't make any difference, as long as it's lubed, what you are already doing is adequate, seeing as you are using a mandrel to expand, sizing and expanding are opposite actions to stretching the case, as you shouldn't have an expander button in there. Trying to partial size the case with an FLS die can lengthen it, as the die shoulder isn't in position to be stopping the case shoulder from pushing back up, as you squeeze the body, think of squeezing a balloon.
				
			 
	








 
 
		 
 
		
