Test & technology: GLOCK 21 Gen4 Cal.45 ACP pistol

The original pistol, developed by GLOCK in 9 Luger, has been followed by various versions for larger ammunition. The first GLOCK 21 Automatic Colt Pistol ACP for .45 ammunition was released in early 1990. GLOCK then began to expand into the US civilian market.


Today, the GLOCK is still known as the “American Dream” pistol. Twenty-five years later, the fourth edition design is out (Gen 4). While technology is the same, the restyling of every G21 generation always introduced some new features.


The Gen4 GLOCK 21, as tested for you, has all of the characteristics of the fourth generation. It has an interchangeable backstrap to suit an individual shooter’s hand size.

Like all fourth-generation models, it uses a telescopic recoil spring to increase the lifetime of the system. GLOCK has varied the texture on the handgrip (RTF3) and the magazine release button has been made bigger.

GLOCK 21 technical details

GLOCK 21 gen4, front view
The solid front has the classic GLOCK design with pyramid sight.
GLOCK 21 gen 4 pistol, back view
The grooving, typical of this model, has a vertical design. The sight is adjustable and has a white outline.

The handgrip design achieves maximum score (- 0 points). The G21 is larger than its other 9 mm counterparts, but the grip and ergonomic finger grooves guarantee excellent handling. The size of the grip can also be changed, using one of the grip panels.

There’s nothing more to be said about cycling operations or safety. Whether fired using one hand or two, or even with a light grip, this pistol works safely and with no problems (- 0 points). The bigger magazine release button is an excellent feature, but like the G41 M.O.S., the GLOCK 21 has a rather heavy slide to release with just the thumb (-1 point). The slide also needs to be larger or have a better grip (-1 point).

The trigger is preloaded for single action. Unfortunately, there is a noticeable rubbing in the initial stage (-3 points). The release point is clear and the weight of the trigger is not excessive.

The sights are excellent – an adjustable rear sight with white outline and a front sight screwed inside (-0 points). There is a perceptible backlash during the preparatory stage (-2 points). The coating of the barrel and metal parts have no marks, while the polymer parts are without any stains or signs of wear.

All of the parts are perfectly assembled. With a 50 mm dispersion, the accuracy falls within the standard of a regular full-size model (-4 points).

The solid barrel, together with a full magazine, means that the weapon has a notable weight – at least for a polymer handgun. However, the pistol is not too heavy when it comes to pointing it.

GLOCK 21 analysis

Accuracy (max. 50 points)46 points
Cycling/safety (max. 10 points)10 points
Trigger characteristics (max. 10 points)7 points
Trigger-grip design (max. 5 points)5 points
Control elements (max. 10 points)
8 points
Sights (max. 5 points)5 points
Workmanship (max. 10 points)8 points
Total score (max. 100 points)89 points
Very good
Rating5 out of 6

GLOCK 21 characteristics

.45 ACP

13 + 1 rounds

Size (L X W X H):193 x 32.5 x 129 mm
Barrel length:
117 mm
Trigger weight:
2.450 g
Weight:1085 g (loaded)
Price:785 euro

Composition: polymer striker-fired pistol, single action, extra grip, rail for accessories.

The GLOCK 21 disassembled into its individual parts
GLOCK 21 disassembled. From the top: slide; barrel with lock; telescopic recoil spring; polymer frame; magazine with 13 round capacity.

GLOCK 21 Gen4 pistol - summary

The GLOCK 21 is to all intents and purposes, a bigger GLOCK 17 in a .45 calibre ACP. It has all of the features of the popular version in 9mm, with more material on the slide and a slightly larger grip. 

The pistol comes in a GLOCK case with two magazines, a loading aid, cleaning kit, and backstrap.

If you’re looking for a GLOCK to suit you, see our GLOCK buyers guide.

For more information about the GLOCK 21, see the manufacturer’s website.

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