COSteve said:
Further, even the 45 Super can't touch the performance of the 10mm in the same platform. Case in point. I handload for my Custom 6" Glock G20/21L in which I shoot both 10mm and 45 Super with just a swap of a barrel and magazines. At the same range, on the same day, with the same magnum pistol powder (Power Pistol) in both, here are some measured results.
10mm: 165gr Speer Gold Dots, Full Charge of Power Pistol - 1,589fps with 925ft/lbs of ME.
45 Super: 200gr Speer Gold Dots, Full Charge of Power Pistol - 1,307fps with 758ft/lbs of ME.
I would be curious what your "full charge" means, because 1590 fps with a full charge of power pistol to me indicates going well over book. Alliant shows 10grs as max for 10mm 165gr Gold Dot @ 1314 fps, and I personally got almost exactly that out of a G20. An extra 1.5" isn't going to give you 275 more FPS unless you're running way over, which I get, I do it too sometimes. In addition, Power Pistol is very good and I find it to be very consistent, but it's not the powder you want to use for absolute max, there are better options.
My fastest 165gr 10mm is using 800x and pushes 1400 fps from a G20 and that's hot, your load (using Power Pistol no less which has much less potential than 800x) is nearly 200 fps faster? You might have got some bad readings.
Also, the .45 Super will flat out whip up on the 10mm, it simply holds more powder and can be loaded identically to the 460 Rowland, but does need a compensated barrel when you move past 10mm territory in order to slow down slide speed.
My hottest 10mm 180gr from a 5" KKM and hottest 45 Super 185gr 5" KKM:
10mm 180gr: 1,387 fps avg (769 ft-lbs)
.45 Super 185gr: 1,570 fps avg (1,012 ft-lbs).
BTW, 200gr XTP from same 5" KKM .45 Super was 1475 fps, so your 1300 fps with 6" apparently isn't nearly as spicy as your 165gr 10mm load, which has to be like 50K psi or something is off.
For heavier stuff, my fastest 200gr WFNGC 10mm was 1315 fps from 5" KKM (800X) and for 5" KKM 45 Super, a 255gr WFNGC at 1320 fps. Same velocity really but over 25% more bullet weight not to mention bigger hole in target (767 ft-lbs vs. 986 ft-lbs)
I'm not dogging 10mm at all nor am I trying to be argumentative, it's just that when you say the .45 Super can't touch the 10mm, that's not true.