Heavier cases should have less internal volume assuming similar external dimensions. This is one reason reloading manuals instruct to reduce max loads when using milsurp brass. Milsurp is generally heavier than civilian due to its use in automatic weapons.
I ran out of SST's before I tried the Nosler cases so I get the apples/ oranges. It just seems odd that I got the results I did. Soon as I get more, I'll be interested to see how fast they are. I'll load up some Sierras in Winchester cases as well. Tried a 40 grain charge with the Sierras and winchester cases figuring on a velocity of 2700 fps ( Sierra data) and got an average of 2850 fps. Apparently I have a quick barrel with Sierras. Spot on with the Hornadys though. Ballistics is anything but boring!