New to this discussion. I just recently started shooting the Glock 39 at my gun range. Never paid much attention to the 45 GAP because I carry a G30. The G30 is a thick, boxy gun. I prefer smaller guns. That is why I bought a Kahr PM45 a year and a half ago. It hasn't proven to be reliable enough for me to carry without my J frame in my pocket. After several thousand rounds and an exchange for a new PM45, and a trip to Karl Sokol, the gun is still not reliable enough for me to trust my life with it. Checked out the G39, 45 GAP. I like it. It works flawlessly. Everything I've been reading about the G39 tells me that it is the same size as the G26/G27. 101 Holsters told me to order G26/G27 holster for the G39. The slide is not the same size a the G30. The G30 is bigger. The recoil of the G39 is soft. It is not snappy. Not expert on ballistics but from what I've read, GAP is same big bullet as ACP in a shorter shell casing. I like big bullets and small guns. Asked my guy at the range to hold a G39 or me.