Chronographed some of my .357 handloads

The notable increase in velocity (30% increase) with slow powder in a longer carbine barrel over a long barreled handgun. The fast burn rate and cast bullet was 10% less of an increase (20%) in the same comparison. I'd be curious to re-do a good load with that cast bullet and a load of H110 in the same formats.

Historically the powers that be have kept a gravitation to fast powders and cast bullets. This has always stumped me except for economy and a low velocity and accurate target or pleasure goal. The fast peak pressure whacks the bullet in the butt and forces it quickly through the rifling as pressure degrades. Slower burn is a more broad and progressive action as your chart eludes. BUT, you cannot push it past the ability of the alloy to take the rifling. Interesting!

Dang Gold Dot clippin along at .444 Marlin speed.
I know some powders are more "economic" but W-296 is my go to for magnums.