For you, which is better? the 45 GAP or the 45 ACP? I once owned a colt series 80 1911 a few years back. it's obviously chambered in 45 ACP and it was good while i was using it til i sold it to a buddy of mine. Now, i own a 45 GAP Glock. the difference for me was the manageable recoil of the 45 GAP. so, i like the GAP better than the ACP. as to bore size, they're just the same. GAPs perform better using 185 grain - 200 grain ammo by federal or speer. at 25 feet, the groupings are pretty much remarkable for the GAP using either the 185 or the 200 grain ammo. As for the guns involved, between the 1911 single action only and the Glock safe action pistol, i must say that im quite biased about it. i still favor the Glocks better than the 1911. But as for the ammo involved, i believe, based on my own experience, the GAPs are better than the ACPs. Plus the fact that i have a small grasp, i have a small hand by the way, i can grip the GAP pistol better than the ACP pistol i had. just my 2 cents.