So question for the reloading experts:
most of the powders we are discussing - CFE223, Leverevolution, N540, BLC2, 2520, etc - are all very close to each other on the burn chart. So why does the pressure curve look different? Is it because of differences in volumetric characteristics of each? For example, does CFE223 have a lower volume requirement than say N540, allowing it to produce lower initial pressure and then generate 'push' further down the barrel?
RE the questions on magazines from @DeSnifter - I can't recommend ASC mags. I'm getting some FTFs w/ them... maybe its something else, not the mag, but its spotty right now.
Burn rate is not linear with pressure. Different powders have different additives and properties which lead to vastly different pressure curves/behaviors. Couple that with cartridge designs and the whole world of internal ballistics and you end up with needing a lot of powder to experiment with to figure out what's best. Burn rate generally gives you a good idea what powders to look at for your goals, assuming you have some starting pressure data from the manufacturer, but beyond that, experimentation is key.
The only thing that sucks about this situation is you can't rely on pressure signs to tell you when you've hit the 52kpsi limit and then back down with cartridges with this size bolt-face requirement; by the time you see pressure signs you're already over the cartridge limit. It's not likely to be destructive immediately, but the bolt will probably wear out more rapidly than ideal. So we have to rely on manufacturer data then try to approximate where powders not tested fall.