Glock 21 Gen4

About the Glock 21 Gen4

The Glock 21 Gen4 is the fourth-generation full-size .45 ACP service pistol from Glock, delivering the stopping power of the .45 Auto round in a polymer-framed, striker-fired platform with a standard 13-round magazine capacity. The Glock 21 was originally introduced in 1990 as Glock's answer to American demand for a .45 ACP pistol, built on a modified Glock 20 (10mm Auto) frame to accommodate the wider .45 cartridge. The Gen4 variant, released in 2012, introduced the modular backstrap system with three interchangeable grip sizes, a dual recoil spring assembly with steel support for reduced felt recoil and extended service life, an enlarged reversible magazine catch, and a more aggressive rough-textured frame. Its octagonal polygonal rifled barrel provides improved accuracy and higher muzzle velocity compared to conventional land-and-groove barrels, while the Safe Action trigger system with three independent passive safeties ensures reliable and safe operation. The Glock 21 remains popular with law enforcement agencies and civilian shooters who prefer the proven .45 ACP cartridge in a high-capacity, lightweight, and reliable modern handgun.

The Glock 21 was Glock's first .45 ACP pistol, introduced in 1990 alongside the Glock 20 (10mm Auto). There was never a Gen1 Glock 21 -- the model postdates the Gen1 era entirely, making all original 1990 examples Gen2 pistols from the start.

Glock 21 Gen4 specifications

The Glock 21 was the first .45 ACP pistol ever produced by Glock, introduced in 1990 alongside the Glock 20 (10mm Auto). Notably, there was no Gen1 Glock 21 -- all original 1990 models were Gen2 pistols, as the Gen1 era (1982-1989) predated the model's existence. The Gen4 dual recoil spring assembly replaced the Gen3's single captive spring, reducing felt recoil by approximately 20% and extending the spring's service life. Weight with empty magazine inserted is 830g. The slide width is 28.5mm (narrower than the 34mm overall frame width). Standard magazine capacity is 13 rounds with optional 10-round magazines available. The Gen4's modular backstrap system includes standard, small, and large grip inserts. The Glock 21 Gen4 has been superseded by the Gen5 MOS variant which adds the Glock Marksman Barrel, nDLC finish, flared magazine well, and optics-ready slide cuts.