Re: difrences in brass
going throught some older posts and saw no replys yet to this one, so I figured I'd better put my .02 in.
Measure the case wall thickness and I think you'll find that the Win is a hair thinner. Also measure all case dimensions and weights before and after sizing, you may find some differences there that may help in finding a pinpoint answer. There is probably not much difference in the composition of the brass, most brass used for cases is about 70/30 alloy and they have that science down pretty well now.
Hope this helps.