Steve4102- Got to disagree with you here and go with Bart. I say the from expirence. Brass is pretty much the same from one manufacter to another. When you size a case ( outside diameter same as others) and put it on a scale.
Brass is an alloy and all manufactures are not identical. This difference in alloy of identical dimensions will not weigh the same.
External dimensions may be identical and they may not. Here is a prime example.
Note, the head/rim of the Rem 300 WSM case is considerable smaller than the Win brass. Weighing and comparing these will tell little to nothing as far as capacity is concerned.
Check out this link. If you scroll down you will find a chart with case weight and case capacity. You will see that there is absolutely not comparison between weight and capacity.
http://www.6mmbr.com/223rem.HTML
Examples from the link.
WCC99 weight = 95.5gr, Capacity = 30.5gr
S&B Weight = 92.3gr, Capacity = 30.5gr
So in this sample the case capacity was identical yet the weight varied by more than 3 grain.
PMP weight = 104.5gr, Capacity = 29.9gr
FNM weight = 97.3gr, capacity = 29.8gr
So, in this sample the case weight varied by a whopping 7.2gr yet the internal capacity only differed by .1 grain.