The first step is to just put your new prospective concealed carry gun in your hand. Does it feel good? If so, then that’s a great first step, since you have a comfortable fit in the hand.
From there, there are two key components of handgun fit.
First is trigger reach, the distance from the back of the grip housing to the trigger face. Imagine a line being drawn straight back from the trigger face to the back of the grip. Essentially, the larger your hands, the longer the optimum trigger reach is going to be just as longer arms require a longer length of pull with a shotgun or rifle.
Consider the relative distance between the back of the grip and the face of the trigger on this Beretta 92A1. Seems pretty big, right? Now here’s a Glock 43.
Doesn’t seem like it’s quite as far, is it? It isn’t; in DA mode, the Beretta has a trigger reach of almost 3 inches; the Glock has a trigger reach of just under 2.6 inches. If you have smaller hands and shorter fingers, the Beretta may be all but unshootable in DA mode, which has LONG been a complaint of the 92 and similar pistols such as the CZ 75.
Second is the shape of your hands. Are yours slight and slender? Or are your fists hammy as heck?
Specifically, look at your pollicis – the muscles that connect to the thumb – and digiti minimi, the muscles at the bottom of the palm running up to the pinkie finger, often called the “heel” of the hand. If you have barely anything there but skin and bones, you’re going to want a bit more palmswell on the grip.
Notice the bump running down the back of the grip on this CZ 75? That’s the palmswell.
How to tell if you need a gun with a larger palmswell is pretty easy. Put the gun in your hand and close your grip around it. If you feel any space between the back of the grip in your hand or find you have to adjust your grip at all, you need a bit more.
Granted, that’s easy with a lot of modern pistols. A common feature on modern handguns is swappable backstraps, so you can get the fit dialed in.
Additionally, the larger your hands, the more backstrap you’ll need to get a good shooting grip.
Not much real estate under the back of the slide on this Glock 26, is there? Look at the CZ 75 up above. There’s a large beaver tail, perfect for getting a high, tight shooting grip. The ergonomics of the CZ 75 have long been one of that pistol’s big selling points as well as a criticism of Glock pistols. Not, of course, that a Glock 9mm is a bad choice of carry gun, it’s just that they aren’t the best choice for SOME people.