Glock Model 21
By R.K. Campbell

Among the most instantly recognizable and widely used handguns today is the Glock. While the Glock pistols that sprang from the original Glock 17 are by far the most numerous, the large frame Glock pistols are also popular. These include the Glock Model 20 10mm and the Glock Model 21 .45 ACP pistol. The first large frame Glock was the 10mm pistol. The Model 21 in .45 ACP was introduced in 1990. This pistol is basically a Model 20 modified and reengineered for the popular .45 caliber Automatic Colt Pistol cartridge (the .45 ACP). The large frame Glock was deemed necessary to compete with other large caliber pistols in police service and to give Glock a contender in the American markets. Americans tend to demand “more caliber” in their defensive handguns. While the Glock Model 21 pistol is similar to the Glock Model 20, there are differences in the slide and frame and of course the magazines differ as well. In other words, one cannot simply change the barrel and magazine and make the 10mm pistol a .45. There is a considerable difference in the energy and cycle curve with the low pressure .45 compared to the high pressure high velocity 10mm and the appropriate springs were needed for proper function with the .45 ACP cartridge. The pistol has been well received. Good reliability and accuracy are good selling points. Another strong point of the Glock 21 is that the magazine holds thirteen rounds of .45 ACP cartridges giving the pistol a total capacity of fourteen cartridges.

A disadvantage of the pistol is its size. The Glock 21 is a large pistol, even bulky, and the grip frame simply does not accommodate smaller hands well. In this author’s experience, most shooters with an average hand size can handle the Glock Model 21, but those with short fingers cannot. Female shooters with small hands but long fingers often do well with the Glock 21 but training and absolute familiarity with the type are essential. While the pistol is large due to the polymer frame the pistol is light enough.

Glock Model 21
Caliber: .45 ACP
Weight: 26 ounces unloaded
Barrel Length: 4.6 inches
Overall length: 7.6 inches
Magazine cap.: 13 rounds

When the whole picture is considered, the Glock offers a considerable amount of firepower in a light package. As an example, the original Colt 1911 Government Model in the same caliber weighs thirty nine ounces. The present service pistol, the Beretta 92 in 9mm, weighs thirty five ounces and offers fifteen rounds of the less effective 9mm cartridge. Other advantages of the Glock include simplicity. The safe action design offers only one trigger action to learn in contrast to double action first shot pistols, which demand the shooter learn both double action and single action fire. There is no manual safety. The lever in the trigger isn’t a true safety but a drop safety intended to prevent inertia from moving the trigger if the pistol is dropped. The Glock safe action trigger is prepped when the slide is racked, with the trigger forward under pressure. The striker or firing pin is partially cocked at this point. By continuing to press the trigger the striker is pressed to the rear and breaks against spring pressure and flies forward firing the pistol. As the slide recoils the action is partially prepped and the pistol may be fired with another short press of the trigger. The Glock safe action has proven reliable in action and offers a trigger that is easily learned quickly. While there is no manual safety, true safety is between the ears and a Glock shooter must understand to keep his finger off of the trigger until he fires.

The Glock Model 21 has proven to be as reliable as the other Glock pistols, which means reliability is held to a high standard. Compared to other .45 ACP pistols, the Glock Model 21 offers moderate felt recoil. Despite the light weight of the pistol, the polymer frame gives a bit in recoil and the large grip distributes recoil out on the palm of the hand. The Glock Model 21 is among the lightest recoiling pistols in .45 ACP caliber. Coupled with a lower bore axis than many pistols, the result is a pistol that is controllable and accurate in combat shooting. The Glock Model 21 is also among the most consistently accurate among Glock pistols. Some Glock types are not noted for good accuracy but the Model 21 often turns in excellent results. Like all quality handguns, the Glock Model 21 prefers one type of ammunition to the other but the level of accuracy demonstrated is often high for a service grade pistol. Cycle reliability is good with all types of ammunition. +P rated ammunition is not recommended for several reasons. First, the Glock has a generous throating of the barrel/chamber area, which relieves the section of the chamber that supports the case head. The result is a feed ramp that feeds practically any bullet design with reliability, however, a +P load may result in a bulged case. Standard .45 ACP ammunition is controllable and effective and +P loads are not needed for military use or personal defense.

A drawback of the Glock pistol is the sights. These plastic sights sometimes snag and are torn lose when drawing or handling the pistols. The front sight and its plastic tab is less than robust. The rear sight is easily dinged as well. The author’s personal Model 21 has been fitted with Trijicon night sights, an excellent addition to any combat pistol. Fitted with self luminous iron sights or ordered with the Glock factory night sights – they are iron as well – the Glock is a far more capable pistol for twenty four hour duty. There are several generations of Glock pistols including those with finger grooves in the frame and with certain improvements. The original Glock Model 21 illustrated is a reliable and effective handgun with many thousands of rounds through it with no problems or malfunctions of any type. When you consider the whole picture, the Glock Model 21 is a worthy combat pistol well worth its modest price.


When testing the Glock Model 21 used in this article, the pistol was deployed in a Don Hume service grade thumbreak holster. This is an excellent all around design that demonstrates a good balance of speed and retention. The holster is molded properly for the Glock, the thumbreak is reinforced to avoid binding and the stitching is professional grade.


The Glock pistol illustrated has fired many thousands of rounds during its service life. For the purposes of this review, we fired the pistol with a variety of service grade ammunition. Five shot groups were fired from a solid benchrest at the 25 yards mark. The pistol turned in good to outstanding accuracy. The Trijicon sights clearly added an advantage, as their sight picture is superior to the factory unit.

Accuracy results, average of three five shot groups, five at seventy five feet:
Black Hills 185 grain JHP: 3.0 inches
Fiocchi 230 grain JHP: 3.5 inches
Hornady 185 grain FTX Critical Defense: 3.25 inches
Winchester 230 grain USA ball: 2.75 inches

This article first appeared in Small Arms Review SAW (May 2013)
and was posted online on March 15, 2013


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