I know all about individual rifles, different lots of components, et cetera. But there's an overarching principle of physics that applies no matter whose finely machined gun or jug of powder or brick of primers we're talking about.
Projectile velocity, and hence kinetic energy, is the manifestation of the work done by an expanding volume of gas. When you study physics you learn this work may be expressed mathematically as the integral of pressure with respect to differential volume.
The deal is if you're hooking a given chamber (257 Wby., 25-06 AI, whatever) to a given length of .257" rifled tube the volume part of the integral is fixed. So the only way to get more work out of it is to increase the height of the pressure function that's being integrated. This is the "area under the curve" thing that gets bandied about.
Ideally we would like to have the powder ignite and have the resulting gas pressure quickly rise to a high but safe level and hold there as long as possible. This would maximize the work done on the projectile. There are new propellants that are supposed to come closer to this ideal than the classics. But this argument has been going on since the classic powders were the only ones available.
Like I said earlier I acknowledge different rifles are different. But my assertion is these differences between rifles are more than likely not big enough to explain the large reported differences in performance without altering the integrand (pressure function) in the work integral in a significant way.
I believe if the rifles in question were properly instrumented to test for pressure the results would support my conjecture.
