Mate, I found a really good 6.5CM brass comparison video here:
https://www.youtube.com/watch?v=FKWGgO4arvUIf you go to about 12.30, you'll see the difference in velocity between Starline small primer and Lapua small primer brass. The velocities are very similar. I guess that means if you work up a load with Lapua brass, the same load could - in theory - work in the Starline brass. Great if you want cheap brass for hunting (Starline) and more expensive stuff for target shooting (Lappy).
I've just bought 200 cases of Lappy and will start working loads up soon. I may buy 100 Starline to see if the same loads work in both brass. If they do, bonus.
Lots of other good info in the video. Interestingly, the Lappy SRP brass has a 0.059" flash hole and the Starline has the bigger 0.080" flash hole, but it doesn't seem to make much difference in velocity. The biggest difference was in the large rifle primer brass, which was notably faster.
Also worth noting, both Lappy and Starline brass have very similar case volumes, which obviously accounts for the similar velocity in loads.
The laws of physics do not apply to politics.