I like full throttle loads. Thanks to Mike McNett who found horsepower to spare with 800-X.
Still, I think loads should be taylored for barrel length. Often a faster powder optimizes a shorter barrel for all around performance.
Consider Mike's 135gr. JHP, 14.5gr 800-X load:
10" barrel, 2022 f/s, 1225 fLbs, PF273, 42 kpsi
5" barrel, 1670 f/s, 836 fLbs, PF 225, 33.1 kpsi per Hodgdon Manual
3.8" barrel, 1596 f/s, 763 fLbs, PF 215, G-29 length.
Clearly slow burning 800-X is efficient in long barrels as presure is increasing with barrel length.
There is a fixed amount of energy in each grain of 800-X. That energy can be computed referencing bullet weight and velocity. If 14.5 gr 800-X completely burns in a 10" barrel, then 462 fLbs of energy is detrimentally expended just beyound a G-29 muzzel. (Blast, flash, soot, smoke, increased perceived recoil (rocket exhaust), and sometimes bullet upset.)
In theory, 9.13gr 800-X within a shortend OAL cartrige will perform similarly to the posted load. (Don't try this at home - much shorter than a 40SW.) That is 5.47gr 800-X wasted, 38% of the 14.5gr charge weight.
You can see why www.imrpowder.com
data for 800-X is so low presure, since their technicians are concerned that most of the powder burns.
All factory loads are subject to the same analysis. I am still searching for the best over all G-29 loads.
Slower moving, heavier bullets are often more efficient in short barrels. Heavier bullets are under presure for a relatively longer time inside any barrel than lighter faster velocity bullets.
If a MAXIMUM power faster burning powder can't be found, a lower charge of a slower burning powder with a more powerfull primer may be the answer for short barreled pistols.
Too bad Glock striker mechanisms are so light and weak. Rifle primers have some potential for 10mm maximum loads.
We need to have Starline produce 10mm brass with an extended and reinforced web and a rifle primer pocket.