Glock 21GEN4

About this product

The Glock 21 Gen4 is Glock's full-size, double-stack .45 ACP duty pistol — the caliber and frame size Glock built specifically for shooters who want more stopping power per round without stepping up to a full-frame 10mm. The Gen4 update carries forward the original G21's size and capacity while adding the interchangeable backstrap system and dual recoil spring assembly that came with the broader Gen4 lineup.

What do you actually get with a Glock 21 Gen4?

This is a striker-fired, polymer-framed semi-auto chambered in .45 ACP with a 13+1 magazine capacity, a 4.61-inch barrel, and an unloaded weight of roughly 26.46 ounces. Overall length runs about 8.23 inches, with a height of 5.47 inches and a width of 1.28 inches — a large-frame pistol built around a big cartridge, not a concealed-carry gun. The barrel uses Glock's octagonal rifling, and the slide is finished in gas-nitride treated steel for corrosion resistance.

What changed with the Gen4 update?

The signature Gen4 features are the dual recoil spring assembly with steel guide rod supports, which was designed to reduce felt recoil and extend service life compared to the single-spring Gen3 setup, plus interchangeable backstraps so shooters with smaller or larger hands can adjust grip circumference to fit. The Gen4 also carries an enlarged, reversible magazine release and more aggressive slide texturing than the original Gen3 G21. It's worth noting the G21 Gen4 has been on the market for years now and has since been joined by newer Glock .45 ACP options in the lineup — buyers who want the latest generation of features should compare current Glock offerings before deciding, but the Gen4 remains a proven, widely-supported platform with a large aftermarket.

Like every Glock, the G21 Gen4 uses the company's simple Safe Action trigger system with no external manual safety beyond the trigger safety, drop safety, and firing pin safety built into the mechanism — the same operating system shooters know from the rest of the Glock lineup, so transitioning from a G17 or G19 to this .45 ACP model feels familiar.

Who is the Glock 21 Gen4 built for?

This is a home-defense and duty-style pistol for shooters who specifically want .45 ACP in a full-size, double-stack platform rather than a single-stack 1911 or a smaller-capacity .45. The size and weight make it better suited to a nightstand, a duty holster, or open carry than to daily concealed carry, though it's been carried concealed by plenty of larger-framed shooters over the years. If your priority is a compact carry gun, Glock's smaller 9mm models will be a better fit; if your priority is a full-capacity .45 ACP platform with a long service record, the G21 Gen4 is a straightforward, no-surprises choice. Holster and magazine compatibility is also broad thanks to how long the G21 platform has been in production, so finding a duty holster, a magazine pouch, or spare magazines is rarely a problem, unlike with a newer or lower-volume pistol.

Because this is a firearm, it cannot ship to your home address. Your order is transferred to a licensed FFL dealer near you, where you'll complete the required paperwork and background check in person before taking possession. California buyers should confirm current state compliance requirements — including magazine capacity, roster status, and any required features — with their FFL before placing an order, since California's rules on handguns and magazine capacity differ from federal requirements and change periodically.

Ammunition for .45 ACP is widely available across most calibers of defensive and range ammunition, and the cartridge has a long track record in both duty and civilian use going back over a century. Recoil in a full-size, double-stack frame like the G21 Gen4 is manageable for most shooters despite the larger cartridge, in part because the added frame mass and dual recoil spring assembly both work to soften the recoil impulse compared to a smaller or lighter .45 ACP platform.