The GAP does fill a very small niche, that being .45 ballistics out of a 9/40 sized frame.
But it is in no way better than the ACP. True, it can match .45 ACP ballistics, but at the cost of higher pressure, less margin for error / safety, more potential pressure problems related to bullet setback, and shorter brass life. It's being pushed to its limits to get those ballistics.
.45 ACP gives those ballistics easily, without pushing the cartridge to it's limits. If you want to push it some, and go to +P levels, then the ACP easily beats the GAP.
But it is in no way better than the ACP. True, it can match .45 ACP ballistics, but at the cost of higher pressure, less margin for error / safety, more potential pressure problems related to bullet setback, and shorter brass life. It's being pushed to its limits to get those ballistics.
.45 ACP gives those ballistics easily, without pushing the cartridge to it's limits. If you want to push it some, and go to +P levels, then the ACP easily beats the GAP.