The .45 GAP

by
posted on December 10, 2012
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
201212101162-45gapblog_m.jpg

The idea is so deceptively simple that I’m surprised someone had not tried it before 2003, which is the year that Gaston Glock did try and success. In a world gone mad over high-capacity magazines on the one hand and big bore pistols on the other, Glock made a monumental effort to give shooters both. Most shooters are uncomfortable with a high-capacity, big-bore pistol and the double-wide magazine that is required. They are much happier with two columns of the shorter 9 mm or 40 S&W rounds. These are the people that I call Capacitonians, those who fill the air with metal and hope for the best. Their opposite number is the Caliberite, the worshiper of cavernous barrels and the massive projectiles that issue forth therefrom. Both would profit mightily from the application of the principles of marksmanship, but that’s another story.

Glock and his designers simply shortened the .45 ACP case to 9 mm/.40 S&W length and inserted a typical .45 ACP bullet over a charge of powder. It used the same type of 9 mm magazine as typical guns of that caliber, of course it held a few less cartridges. Mechanically, the new pistol had to have a stronger, heavier slide and other mechanical modifications. But these were possible and Glock got them done. They offered small, medium and large versions of what was essentially the world’s first 9 mm-sized .45. The new cartridge was called the .45 GAP (Glock Auto Pistol) and ammunition makers started loading it quickly.

They say the measure of a cartridge is how many ammo makers produce the ammo and how many gunmakers build a gun for the caliber. Most ammo makers offer a .45 GAP round, but no other gunmakers currently offer a pistol in that caliber. There were a few XDs from Springfield and some really neat experimentals from Para, but if you want a pistol for your .45 GAP ammo, you have go to the source—Glock.

In short, the idea has not caught on particularly well. I believe Glock still sells respectable quantities of the guns, but there is no other option for the caliber. Most of that seems to be because “simply shortened the .45 ACP case” does not completely describe what happened. The designers had to fiddle with nearly every dimension of that case to make it work right and they obviously reduced case capacity. That simply means that a .45 GAP pistol will essentially reproduce .45 ACP ballistics—a 230-grain slug at 850 fps—but it does so at a sharply increased pressure level. And too much pressure is very hard on pistols—very hard.

Latest

jammed cartridge in chamber
jammed cartridge in chamber

Rifleman Q&A: Understanding a Firearm's Cycle of Operation

The cycle of operation is the mechanical sequence of events that it takes to fire one shot out of a firearm. If one of those steps fails to take place as designed, there is an interruption in the cycle of operation and the gun stops firing.

Review: Sightmark Pinnacle 1-6x24 mm Riflescope

Looking for a performance LPVO without the usual associated cost? The Sightmark Pinnacle 1-6x24 mm might be your answer.

Myths & Misunderstandings About the “Modern Fighting 1911”

The Colt Model 1911 pistol and its derivatives are among the most iconic military handguns ever made. But in 2026, does the M1911 still hold up as a quality defensive arm?

Heir Apparent: The CZ 600+ Carbine

CZ's 527 action was long a popular option scaled around compact cartridges like the .223 Remington and the 7.62x39 mm. Now, the new CZ 600+ Carbine brings that same concept to the company's new CZ 600 series.

I Carry: Smith & Wesson Model 386 Night Guard in an ANR Design Holster

In our latest "I Carry" setup, we're featuring the Smith & Wesson Model 386 Night Guard in an ANR Design holster, and we've got a Streamlight EDC flashlight to round out our kit.

The Armed Citizen® Oct. 23, 2026

Read today's "The Armed Citizen" entry for real stories of law-abiding citizens, past and present, who used their firearms to save lives.

Interests



Get the best of American Rifleman delivered to your inbox.