45 GAP: Glock's Failed Update of the .45 ACP

Give Glock credit where it’s due— introducing a new cartridge into the U.S. market and declaring it the replacement for America’s favorite pistol cartridge, the .45 ACP, takes guts. Anything that tries to supplant the .45 ACP as our go-to big-bore pistol cartridge had better bring some serious credentials to change our minds. The 45 GAP (Glock Automatic Pistol) had credentials to spare; Glock’s custom pistol cartridge was smaller, faster, and just as powerful as the old-school .45 ACP.

That was in 2003. You might have noticed that practically nobody is shooting it 20 years later. Hell, hardly anyone used it in the beginning. Why didn’t such an innovative cartridge catch on? After all, it blended many traits American shooters love about 9mm and .45 ACP, two of the best-selling pistol cartridges in the U.S.

Let’s dig into where this cartridge came from, its performance, and what went wrong.

Anything that attempts to supplant the .45 ACP has a lot of ground to cover.

History of the 45 GAP

The 45 GAP was the brainchild of the famous Austrian gunmaker Glock and ammunition manufacturer Speer. The two companies sought to create a cartridge that offered on-target effects similar to the .45 ACP but with the shorter case length of a 9mm or .40 S&W to work with smaller-framed pistols.

The overall cartridge length depends on the bullet, but according to the Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) standards, the case is 0.128 inches shorter than a .45 ACP case.

Shortening the .45 ACP’s case was simple enough, but losing powder behind a big-bore bullet would typically result in a slower, less effective cartridge. Glock and Speer solved the problem by using a different primer and propellant to achieve more pressure.

The formula worked, and the 45 GAP matched the .45 ACP in many ballistic fields. Glock introduced the new cartridge in 2003 alongside three pistols chambered for the new cartridge.

Police departments were among the 45 GAP’s biggest advocates. At the time, the 45 ACP was a popular choice for law enforcement, and some officers complained that the long, fat cartridge required grips that were too large for their hands.

According to American Handgunner, New York, Pennsylvania, Georgia, South Carolina, and Florida state law enforcement agencies jumped at the opportunity to switch to the shorter .45-caliber round.

The trend was short-lived, though. By 2020, New York and Pennsylvania reverted to using .45 ACP; Georgia and South Carolina opted for 9mm. The following year, Florida made the 9mm Glock 45 the official duty weapon of the Florida Highway Patrol.

What doomed the 45 GAP? As is often the case, the answer lies in a combination of factors. For one, new cartridges always have to prove market demand exists before ammunition manufacturers invest in them at the expense of proven cartridges.

When push came to shove, manufacturers couldn’t justify scaling back existing breadwinners to take a chance on the unproven Glock cartridge.

At the same time, the firearm industry found other solutions to the problems the round attempted to solve. It turns out that hot-rodding 9mm ammunition to hit harder is a lot easier than selling the public on a new cartridge. Gunmakers also got better at making compact handguns with thinner, stronger materials. A full-size .45 ACP handgn — some double-stacks and definitely single-stacks — can have nearly the same size grip as a full-size 9mm. Just like that, the 45 GAP became redundant.

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45 GAP Performance

According to SAAMI, the 45 GAP produces 23,000 psi of chamber pressure. That’s enough to achieve a muzzle velocity of 1,020 fps with a 200-grain bullet. A 230-grain Winchester jacketed hollow point, on the other hand, achieves a muzzle velocity of 880 fps and muzzle energy of 395 ft-lb.

These traits and terminal effects vary depending on the specific ammunition you’re using, but the 45 GAP is a powerful cartridge.

Judging by the ballistic data, the 45 GAP is great at doing its job, but problems become apparent when you start loading rounds into a magazine. While the 45 GAP is significantly shorter than the .45 ACP, its diameter is the same. That means it has the same magazine capacity issues that plague all big-bore pistol cartridges.

For example, the full-size 45 GAP Glock 37 uses a 10-round magazine. The full-size 9mm Glock 17 has nearly identical exterior dimensions but comes with a standard 17-round magazine.

Then again, finding 45 GAP ammunition can present a challenge, so magazine capacity might be the least of your concerns.

Stacking Up Against the .45 ACP

If you placed a 45 GAP cartridge and a .45 ACP cartridge next to each other, you’d probably assume that the stubby 45 GAP would be much slower and less powerful, but you would be wrong.

The 45 GAP isn’t a .45 short; it’s a different cartridge altogether. The people at Glock and Speer know that it’s what’s inside that counts. The 45 GAP’s more modern (and powerful) primer and powder generates 2,000 psi more pressure than the .45 ACP. Its 23,000-psi chamber pressure is actually on par with a juiced-up .45 ACP +P round.

As a result, the 45 GAP’s muzzle velocity and muzzle energy are actually superior to those of the .45 ACP. When comparing 200-grain bullets, 45 GAP is the winner.

That advantage doesn’t exist across the board, though. As bullet weight increases, the 45 GAP loses steam, and .45 ACP does a better job of firing its standard load — a 230-grain bullet.

At this point, the scarcity of 45 GAP ammunition alone is enough to keep you away from the round, let alone the fact that Glock is the only company that makes a gun for it. Contrastingly, there are tons of .45 ACP guns out there, and lots and lots of ammo options.

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Guns That Shoot 45 GAP

If you want a pistol that shoots 45 GAP, you’d better like grips shaped like Lego bricks. Glock is still building three sizes of pistols in the chambering, but other manufacturers apparently aren’t interested. All three Glock pistols retail for $560.

Springfield also dipped a toe into the market from 2005 to 2007, so you might also be able to find a used XD chambered for 45 GAP.

Glock 37

The Glock G37 is a “quantum leap in big-bore technology.”

Glock calls the Glock G37 “a quantum leap in big-bore technology.” While that may sound optimistic, you always know what you’re getting from a Glock, and it’ll at least shoot consistently and reliably. The full-size Glock G37 comes with a 4.5-inch barrel, an 8-inch overall length, standard white painted sights, and a 10+1 capacity.

Glock 38

g38 — The Glock G38 is about the same size as the popular Glock 19, only with a little more punch.

The compact Glock G38 offers the 45 GAP’s punch in a size comparable to the best-selling 9mm Glock 19. This reduced size is due to its 4-inch barrel and 8-round magazine, although a 10-round magazine will work with the Glock 38.

Glock 39

g39 — The Glock G39 is the smallest pistol Glock chambers in 45 GAP.

The smallest 45 GAP pistol you can buy is the micro-compact Glock G39. This carry pistol has a 3.4-inch barrel and a tiny grip, so its utility is fairly limited. The standard capacity is 6+1, but 8- and 10-round magazines fit, too.

Parting Shots

glock in box — Although 45 GAP took several good swings at .45 ACP, it couldn’t successfully dethrone the all-American cartridge.

The 45 GAP is proof that in the world of firearms, success is largely a popularity contest. Glock didn’t just take a swing at one of the most widely used cartridges in the U.S. market, it attempted to dethrone a cultural icon. Many people who shoot .45 ACP don’t just like the round’s ballistics, they take pride in keeping the all-American cartridge’s tradition alive.

That’s too bad because the cartridge is a natural evolution of the 45-caliber family. It does a good job of combining the best characteristics of .45 ACP and 9mm. It flies fast and hits hard. Fortunately, it’s still in production, and you can still buy a brand-new pistol from Glock if you want in on the action. If enough people do that, the potent 45 GAP can avoid going the way of the 357 SIG.