In all my reloading exsperiences the closer to the max you get the more speed you gain as you add powder EXAMPLE:
50 grains of powder gives you 2900FPS and for ever .5 grains you add 30-35fps until it gets close to max then it usually jumps so that your getting the same speed increase with .2 or .3 that you were with .5
I found my guns sweet spot and it was up at max and it shoots REALLY well. but when the temp goes up I have to back it off a little to stay safe for me and the gun. My Max load is shooting 3125 FPS with 50.3 grains of powder. on the same day I found my sweet spot with a smaller charge of 49.0 grains and it chrono's 3085 FPS. I just don't understand how I can take a max load back it off 1.3 grains and it only dropped 40fps??? anyone have an answer or am I looking into this way to much??
Quit over thinking it. If shooting good enjoy it. Over the years have seen some odd things in reloading, I think sometimes it is just the culmination of the combination of gun, barrel, caliber, bullet, powder, etc. that gives oddities to scratch our heads over.
Some combo's will plateau in velocity when you hit max. pressure. Powder burn often gets less efficient.
375's right... quit overthinking it. Get a big enough caliber that you can allow for temp. swings in your loading and shoot the pipe.