By Patrick Sweeney, Gun Digest
This one has had me scratching my head ever since I first saw it, back at the 2007 SHOT show. Basically, the round is an engineering double-down on the .40, as in make a .45 that is short enough to fit into a 9mm magazine tube. Alas, it is an engineering step too far.
Advantages? You have a .45-caliber bullet. In the first loadings, they were only 200 grains, but, with a little wizardry, the ballisticians were able to get a full 230-grain bullet stepping out at full .45 ACP velocities. Nice.
You’d think, being in a G17-sized pistol, that it would be harder to control than a .45 ACP in a G21. Not really. The large grip of the G21 introduces problems of its own, and the end result is that the G37 is actually more controllable.
Disadvantages? The extra bullet diameter cuts into magazine capacity. Where the G22 holds 15 rounds of .40 S&W, the G37 only holds 10 rounds of .45 GAP.
The brass is easily mistaken for .45 ACP, so reloaders at your gun club will hate you mightily for leaving your brass. Also, the .45 GAP absolutely cannot be accommodated with a slide of the same weight as a 9mm/.40, so Glock had to increase the slide width. That means your G37 has to have a G37-specific holster, though magazines are the same externally.
The lineup here is G37, G38, and G39. Of the three, the only one to consider is the G38. If you’re going to have the size of the G37, you might as well have the capacity of a G22, while the big bullets in the ultra-compact G39 will be an unpleasant recoil experience.