I am looking at a Para-ord Carry GAP for a future purchase.
http://www.paraord.com/product/product.html?id=105
The 45 GAP case has a higher pressure capacity than a 45 ACP. I have a semi-dangerous idea that I can recover some of the lost velocity of the 3" barrel by loading a GAP to "+P" levels. The GAP case with its small primer is more suited for this type of KB tempting than the large primer ACP.
Ballisticly, the 45 GAP is the same as a 45 ACP. It is the same bullet at the same muzzle velocity. Therefore, its terminal performance is expected to be the same. This makes it an effective caliber for personal defense.
There have not been any platforms that take advantage of its shorter case, namely a smaller size or higher capacity 45. So the caliber has yet to stand out, but this is not due to its capability.