Possibly in your world but I don't think so in the real world!
ballistically almost identical if comparing same weight/type projectiles, Very simply if you push the same weight/ diameter projectile at the same velocity then you get the same basic performance, there should be no disagreement on that.
Pressures they operate at are virtually identical, as for a smaller package you are comparing a OAL of 45 GAP at 1.137== the 45 ACp is 1.275, not much difference at all.
as the magazines are the same size or near then that's what the gun has to fit around.
The reason they are hard to find its another cartridge that is in search of solution where there is no problem.
Not sure what the first sentence is even referring too...
Quote from online:
"The .45 GAP has the same diameter as the .45 ACP pistol cartridge but is slightly shorter, and uses a small-pistol primer instead of the large-pistol primer most commonly used in .45 ACP ammunition. Originally, the maximum bullet weight of the .45 GAP was 200 grains (13 g). In order to provide terminal ballistics that matched the standard 230-grain (15 g) .45 ACP loads, the .45 GAP was designed to operate at a higher standard pressure-roughly equivalent to the higher pressures found in .45 ACP "+P" rounds. Since the .45 GAP has a much smaller cartridge volume than the .45 ACP, the desired pressure and resulting velocity needed to be achieved through powder selection alone. Later development concluded that the .45 GAP could also fire 230-grain (15 g) ammunition as does the .45 ACP."
Thank you come again.

