The Glock is a series of polymer-framed, short recoil-operated, locked-breech semi-automatic pistols designed and produced by Austrian manufacturer Glock Ges.m.b.H. It entered Austrian military and police service by 1982 after it was the top performer in reliability and safety tests.^[5]

Despite initial resistance from the market to accept a perceived "plastic gun" due to both unfounded durability and reliability concerns, as well as fears that its use of a polymer frame might circumvent metal detectors in airports, Glock pistols have become the company's most profitable line of products as well as supplying national armed forces, security agencies, and police forces in at least 48 countries.^[6] Glocks are also popular firearms among civilians for recreational and competition shooting, home- and self-defense, and concealed or open carry.^[7]

The company's founder, head engineer Gaston Glock, had no experience with firearms design or manufacture at the time their first pistol, the Glock 17, was being prototyped. Glock did, however, have extensive experience in advanced synthetic polymers, knowledge of which was instrumental in the company's design of the first commercially successful line of pistols with a polymer frame.^[8] Glock introduced ferritic nitrocarburizing into the firearms industry as an anticorrosion surface treatment for metal gun parts.^[9]

In 1980, the Austrian Armed Forces announced that it would seek tenders for a new, modern duty pistol to replace their World War II–era Walther P38 handguns.^[10] The Austrian Ministry of Defence formulated a list of 17 criteria for the new generation service pistol, including requirements that it would be self loading; fire the NATO-standard 9×19 mm Parabellum round; the magazines were not to require any means of assistance for loading; be secure against accidental discharge from shock, strike, and drop from a height of 2 m onto a steel plate.^[5] After firing 15,000 rounds of standard ammunition, the pistol was to be inspected for wear. The pistol was to then be used to fire an overpressure test cartridge generating 5,000 bar (500 MPa; 73,000 psi). The normal maximum operating pressure (Pmax) for the 9mm NATO is 2,520 bar (252 MPa; 36,500 psi).^[11]

Glock became aware of the Austrian Army's planned procurement, and in 1982 assembled a team of Europe's leading handgun experts from military, police, and civilian sport-shooting circles to define the most desirable characteristics in a combat pistol.^[5] Within three months, Glock developed a working prototype that combined proven mechanisms and traits from previous pistol designs.^[12] In addition the plan was to make extensive use of synthetic materials and modern manufacturing technologies, to make it a very cost-effective candidate.

Several samples of the 9×19mm Glock 17 (so named because it was the 17th patent procured by the company^[13]) were submitted for assessment trials in early 1982, and after passing all of the exhaustive endurance and abuse tests, the Glock emerged as the winner.^[14][15][16]

The handgun was adopted into service with the Austrian military and police forces in 1982 as the P80 (Pistole 80),^[17] with an initial order for 25,000 guns.^[12] The Glock 17 outperformed eight different pistols from five other established manufacturers (Heckler & Koch of Germany offered their P7M8, P7M13, and P9S, SIG Sauer of Switzerland bid with their P220 and P226 models, Beretta of Italy submitted their model 92SB-F, FN Herstal proposed an updated variant of the Browning Hi-Power, and the home-grown Steyr Mannlicher entered the competition with the GB).^[18]

The results of the Austrian trials sparked a wave of interest in Western Europe and overseas, particularly in the United States, where a similar effort to select a service-wide replacement for the M1911 had been going on since the late 1970s (known as the Joint Service Small Arms Program). In late 1983, the United States Department of Defense inquired about the Glock pistol and received four samples of the Glock 17 for unofficial evaluation.^[19] Glock was then invited to participate in the XM9 Personal Defense Pistol Trials, but declined because the DOD specifications would require extensive retooling of production equipment and providing 35 test samples in an unrealistic time frame.^[19]

Shortly thereafter, the Glock 17 was accepted into service with the Norwegian and Swedish armed forces, surpassing all prior NATO durability standards.^[19] As a result, the Glock 17 became a standard NATO-classified sidearm and was granted a NATO stock number (1005-25-133-6775).^[19] By 1992, some 350,000 pistols had been sold in more than 45 countries, including 250,000 in the United States alone.^[17]

Starting in 2013 the British Army began replacing the Browning Hi-Power pistol with the Glock 17 Gen 4, due to concerns about weight and the external safety of the Hi-Power.^[20]

Glock has updated its basic design several times throughout its production history.

A mid-life upgrade to the Glock pistols involved the addition of checkering on the front strap and serrations to the back strap. These versions, introduced in 1988, were informally referred to as "second-generation" models. To meet American ATF regulations, a steel plate with a stamped serial number was embedded into the receiver in front of the trigger guard. In 1991, an integrated recoil spring assembly replaced the original two-piece recoil spring and tube design. The magazine was slightly modified, changing the floorplate and fitting the follower spring with a resistance insert at its base.

In 1998, the frame was further modified with an accessory rail (called the "Universal Glock rail") to allow the mounting of laser sights, tactical lights, and other accessories. Thumb rests on both sides of the frame and finger grooves on the front strap were added. Glock pistols with these upgrades are informally referred to as (early) "third-generation" models. Later third-generation models additionally featured a modified extractor that serves as a loaded chamber indicator, and the locking block was enlarged, along with the addition of an extra cross pin to aid the distribution of bolt thrust forces exerted by the locking block. This cross pin is known as the locking block pin and is located above the trigger pin.^[21]

The polymer frames of third-generation models can be black, flat dark earth, or olive drab. Besides that, non-firing dummy pistols ("P" models) and non-firing dummy pistols with resetting triggers ("R" models) have a bright red frame and Simunition-adapted practice pistols ("T" models) – a bright blue frame for easy identification.^[22]

In 2009, the Glock 22 RTF2 (Rough Textured Frame 2) (chambered in .40 S&W) was introduced. This pistol featured a new checkering texture around the grip and new scalloped (fish gill-shaped) serrations at the rear of the sides of the slide.^[23][24] Many of the existing models became available in the RTF2 version, including the 31, 32, 23, 21, 19. Some of those did not have the fish gills.

At the 2010 SHOT Show, Glock presented the "fourth generation", now dubbed "Gen4" by Glock itself. Updates centered on ergonomics and the recoil spring assembly. The initial two fourth-generation models announced were the full-sized Glock 17 and Glock 22, chambered for the 9×19 mm Luger and .40 S&W cartridges, respectively. The pistols were displayed with a modified rough-textured frame, grip checkering, and interchangeable backstraps of different sizes. "Gen4" is rollmarked on the slide next to the model number to identify the fourth-generation pistols.

The basic grip size of the fourth-generation Glock pistols is slightly smaller compared to the previous design. A punch is provided to remove the standard trigger housing pin and replace it with the longer cross pin needed to mount the medium or large backstrap that will increase the trigger distance by 2 mm (0.079 in) or 4 mm (0.16 in). With the medium backstrap installed, the grip size is identical to the third-generation pistols. The magazine release catches are enlarged and reversible for left-handed use. To use the exchangeable magazine release feature, fourth-generation Glock magazines have a notch cut on both sides of the magazine body. Earlier versions of the magazines will not lock into the Gen4 pistols if the user has moved the magazine release button to be operated by a left-handed user. Gen4 magazines will work in older models.^[25]

Mechanically, fourth-generation Glock pistols are fitted with a dual recoil spring assembly to help reduce perceived recoil and increase service life expectancy. Earlier subcompact Glock models such as the Glock 26 and Glock 30 have already used a dual recoil spring assembly which was carried over to the fourth-generation versions of those models. The slide and barrel shelf have been resized, and the front portion of the polymer frame has been widened and internally enlarged, to accommodate the dual recoil spring assembly. The trigger mechanism housing has also been modified to fit into the smaller-sized grip space.^{[26][27][28][29][30]}

The introduction of fourth-generation Glock pistols continued in July 2010 when the Glock 19 and Glock 23, the reduced size "compact" versions of the Glock 17 and Glock 22, became available for retail.^[31] In late 2010, Glock continued the introduction of fourth-generation models with the Glock 26 and Glock 27 "subcompact" variants.

In January 2013, more fourth-generation Glock pistols were introduced commercially during the annual SHOT Show, including the Glock 20 Generation 4 along with other fourth-generation Glock models.

In September 2011, Glock announced a recoil spring exchange program in which the manufacturer voluntarily offers to exchange the recoil spring assemblies of its fourth-generation pistols (with the exception of the "subcompact" Glock 26 and Glock 27 models) sold before 22 July 2011 at no cost "to ensure our products perform up to GLOCK’s stringent standards", according to the company.^[32]

On 29 June 2016 the United States Federal Bureau of Investigation (FBI) awarded a contract to Glock to provide new 9×19mm Parabellum chambered duty pistols.^[33] The solicitation specifications deviated from the specifications of Glock fourth-generation models.^[34]

In August 2016 the Indianapolis Metro Police Department (IMPD) started training with a batch of Glock 17M pistols. The most obvious difference with the Glock third and fourth-generation models on published images is the omission of finger grooves on the grip.^[35] The IMPD issued a Glock 17M voluntary recall following failures encountered while dry firing the pistols during training. According to Major Riddle with the IMPD; "Glock is working to correct the problem and we hope to begin issuing the new [17Ms] as soon as December".^[36][37]

In August 2017, Glock presented the "fifth generation" or "Gen5". The revisions centered on ergonomics and improving reliability. Many parts of fifth-generation Glock pistols cannot be interchanged with those of the previous generations. The two fifth-generation models announced were the Glock 17 and Glock 19, chambered for the 9×19 mm Parabellum. Some conspicuous changes on the fifth-generation models are: ambidextrous slide stop levers, nDLC (Diamond-Like Carbon) surface finish for barrel and slide, a barrel featuring a revised style of polygonal rifling (called the "Glock Marksman Barrel" by Glock), a deeper recessed barrel crown, omission of the finger grooves on the grip, a flared magazine well, and a reintroduction of a (half moon shaped) cutout on the bottom front of the grip. The locking block pin located above the trigger pin that was introduced in the third generation is omitted. Many internal parts were less conspicuously revised.^{[38][39][40][41][42]} "Gen 5" is rollmarked on the slide next to the model number to identify the fifth-generation pistols. The magazines were also revised for the fifth-generation models. The redesigned magazine floor plates feature a frontward protruding lip to offer grip for manual assisted extraction and the magazine follower became orange colored for easier visual identification.

The Glock 17 is a 9 mm short recoil–operated, locked-breech semi-automatic pistol that uses a modified Browning cam-lock system adapted from the Hi-Power pistol.^[43] The firearm's locking mechanism uses a linkless, vertically tilting barrel with a rectangular breech that locks into the ejection port cut-out in the slide. During the recoil stroke, the barrel moves rearward initially locked together with the slide about 3 mm (0.12 in) until the bullet leaves the barrel and chamber pressure drops to a safe level. A ramped lug extension at the base of the barrel then interacts with a tapered locking block integrated into the frame, forcing the barrel down and unlocking it from the slide. This camming action terminates the barrel's movement while the slide continues back under recoil, extracting and ejecting the spent cartridge casing. The slide's uninterrupted rearward movement and counter-recoil cycle are characteristic of the Browning system.^[44]

Glock pistols incorporate a number of features intended to enhance reliability in adverse conditions, such as utilizing advanced metal coatings, "stub" slide guides instead of true frame rails, and an unusual cocking mechanism wherein the trigger is partially responsible for cocking the striker.^[45] By relying partially on force from the shooter's trigger finger to cock the striker, a Glock effectively reduces the load on the recoil spring as the slide moves forward into battery, whereas almost all other striker-fired pistols on the market rely fully on the recoil spring to cock the striker. This design gives the recoil spring fewer tasks as the action cycles, helping to ensure that sufficient energy is available to strip a new round from the magazine and achieve full battery even when the breech, chamber, and/or magazine are heavily fouled. For these and other reasons, Glock pistols are commonly considered to be some of the most reliable striker-fired, semi-automatic handguns available, with some independent testing even showing a Glock taking a narrow lead over a Sig Sauer P320^[46] in a wet/dry reliability test, even after the latter became a de facto industry standard for reliability after being selected as the winner of the U.S. Army's MHS competition.

The slide features a spring-loaded claw extractor, and the stamped sheet metal ejector is pinned to the trigger mechanism housing.^[47] Pistols after 2002 have a reshaped extractor that serves as a loaded chamber indicator. When a cartridge is present in the chamber, a tactile metal edge protrudes slightly out immediately behind the ejection port on the right side of the slide.^[48] The striker firing mechanism has a spring-loaded firing pin that is cocked in two stages that the firing pin spring powers. The factory-standard firing pin spring is rated at 24 N (5.4 lbf), but by using a modified firing pin spring, it can be increased to 28 N (6.3 lbf) or to 31 N (7.0 lbf).^[49] When the pistol is charged, the firing pin is in the half-cock position. As the trigger is pulled, the firing pin is then fully cocked. At the end of its travel, the trigger bar is tilted downward by the connector, releasing the firing pin to fire the cartridge. The connector resets the trigger bar so that the firing pin will be captured in half-cock at the end of the firing cycle. This is known as a preset trigger mechanism, referred to as the "Safe Action" trigger by the manufacturer. The connector ensures the pistol can only fire semiautomatically.

The factory-standard, two-stage trigger has a trigger travel of 12.5 mm (0.49 in) and is rated at 25 N (5.6 lbf), but by using a modified connector, it can be increased to 35 N (7.9 lbf) or lowered to 20 N (4.5 lbf). In response to a request made by American law enforcement agencies for a two-stage trigger with increased trigger pull, Glock introduced the NY1 (New York) trigger module, which features a flat spring in a plastic housing that replaces the trigger bar's standard coil spring. This trigger modification is available in two versions: NY1 and NY2 that are rated at 25 N (5.6 lbf) to 40 N (9.0 lbf) and 32 N (7.2 lbf) to 50 N (11.2 lbf), respectively, which require about 20 N (4.5 lbf) to 30 N (6.7 lbf) of force to disengage the safeties and another 10 N (2.2 lbf) to 20 N (4.5 lbf) in the second stage to fire a shot.

The Glock's frame, magazine body, and several other components are made from a high-strength nylon-based polymer invented by Gaston Glock, called Polymer 2.^[50] This plastic was specially formulated to provide increased durability and is more resilient than carbon steel and most steel alloys. Polymer 2 is resistant to shock, caustic liquids, and temperature extremes where traditional steel/alloy frames would warp and become brittle.^[50] The injection-molded frame contains four hardened steel guide rails for the slide: two at the rear of the frame, and the remaining pair above and in front of the trigger guard. The trigger guard itself is squared off at the front and checkered. The grip has an angle of 109° and a nonslip, stippled surface on the sides and both the front and rear straps.^[51] The frame houses the locking block, which is an investment casting that engages a 45° camming surface on the barrel's lower camming lug. It is retained in the frame by a steel axis pin that holds the trigger and slide catch. The trigger housing is held to the frame by means of a polymer pin. A spring-loaded sheet-metal pressing serves as the slide catch, which is secured from unintentional manipulation by a raised guard molded into the frame.

The Glock pistol has a relatively low slide profile, which holds the barrel axis close to the shooter's hand and makes the pistol more comfortable to fire by reducing muzzle rise and allows for faster aim recovery in rapid firing sequences. The rectangular slide is milled from a single block of ordnance-grade steel using CNC machinery.^[52] The barrel and slide undergo two hardening processes prior to treatment with a proprietary nitriding process called Tenifer. The Tenifer treatment is applied in a 500 °C (932 °F) nitrate bath.^[50] The Tenifer finish is between 0.04 and 0.05 mm (0.0016 and 0.0020 in) in thickness, and is characterized by extreme resistance to wear and corrosion; it penetrates the metal, and treated parts have similar properties even below the surface to a certain depth.^[53]

The Tenifer process produces a matte gray-colored, nonglare surface with a 64 Rockwell C hardness rating and a 99% resistance to salt water corrosion (which meets or exceeds stainless steel specifications),^[52] making the Glock particularly suitable for individuals carrying the pistol concealed as the highly chloride-resistant finish allows the pistol to better endure the effects of perspiration.^[53] Glock steel parts using the Tenifer treatment are more corrosion resistant than analogous gun parts having other finishes or treatments, including Teflon, bluing, hard chrome plating, or phosphates.^[53] During 2010 Glock switched from the salt bath nitriding Tenifer process to a not exactly disclosed gas nitriding process. After applying the nitriding process, a black Parkerized decorative surface finish is applied. The underlying nitriding treatment will remain, protecting these parts even if the decorative surface finish were to wear off.^[9]

A current production Glock 17 consists of 34 parts.^[49] For maintenance, the pistol disassembles into five main groups: the barrel, slide, frame, magazine, and recoil-spring assembly. The firearm is designed for the NATO-standard 9×19mm Parabellum pistol cartridge, but can use high-power (increased pressure) +P ammunition with either full-metal-jacket or jacketed hollow-point projectiles.

The hammer-forged barrel has a female type polygonal rifling with a right-hand twist. The stabilization of the round is not by conventional rifling, using lands and grooves, but rather through a polygonal profile consisting of a series of six or eight interconnected noncircular segments (only the .45 ACP and .45 GAP have octagonal polygonal rifling). Each depressed segment within the interior of the barrel is the equivalent of a groove in a conventional barrel. Thus, the interior of the barrel consists of smooth arcs of steel rather than sharply defined slots.

The method by which Glock barrels are rifled is somewhat unusual; instead of using a traditional broaching machine to cut the rifling into the bore, the Glock process involves beating a slowly rotating mandrel through the bore to obtain the hexagonal or octagonal shape.^[54] As a result, the barrel's thickness in the area of each groove is not compromised as with conventional square-cut barrels. This has the advantage of providing a better gas seal behind the projectile as the bore has a slightly smaller diameter, which translates into more efficient use of the combustion gases trapped behind the bullet,^[54] slightly greater (consistency in) muzzle velocities, and increased accuracy and ease of maintenance.^[55]

Glock pistols lack a traditional on-off safety lever, which Glock markets as an advantage, especially to police departments, as the user is able to fire immediately without separately manipulating a safety.^[56] Instead, the pistols are designed with three independent safety mechanisms to prevent accidental discharge. The system, designated "Safe Action" by Glock, consists of an external integrated trigger safety and two automatic internal safeties: a firing pin safety and a drop safety.^[57] The external safety is a small inner lever contained in the trigger. Pressing the lever activates the trigger bar and sheet metal connector. The firing pin safety is a solid hardened steel pin that, in the secured state, blocks the firing pin channel (disabling the firing pin in its longitudinal axis). It is pushed upward to release the firing pin for firing only when the trigger is actuated and the safety is pushed up through the backward movement of the trigger bar. The drop safety guides the trigger bar in a ramp that is released only when direct rearward pressure is applied to the trigger. The three safety mechanisms are automatically disengaged one after the other when the trigger is squeezed, and are automatically reactivated when the trigger is released.^[17][58]

In 2003, Glock announced the Internal Locking System (ILS) safety feature. The ILS is a manually activated lock located in the back of the pistol's grip. It is cylindrical in design and, according to Glock, each key is unique. When activated, the lock causes a tab to protrude from the rear of the grip, giving both a visual and tactile indication as to whether the lock is engaged or not. When activated, the ILS renders the Glock unfireable, as well as making it impossible to disassemble. When disengaged, the ILS adds no further safety mechanisms to the Glock pistol. The ILS is available as an option on most Glock pistols. Glock pistols cannot be retrofitted to accommodate the ILS. The lock must be factory-built in Austria and shipped as a special order.

The Glock 17 feeds from staggered-column or double stack magazines that have a 17-round capacity (which can be extended to 19 with an optional floor plate) or optional 33-round high-capacity magazines.^[59] For jurisdictions which restrict magazine capacity to 10 rounds, Glock offers single-stack, 10-round magazines. The magazines are made of steel and are overmolded with plastic. A steel spring drives a plastic follower. After the last cartridge has been fired, the slide remains open on the slide stop. The slide stop release lever is located on the left side of the frame directly beneath the slide and can be manipulated by the thumb of the right-handed shooter.

Glock magazines are interchangeable between models of the same caliber, meaning that a compact or subcompact pistol will accept magazines designed for the larger pistols chambered for the same round. However, magazines designed for compact and subcompact models will not function in larger pistols because they are not tall enough to reach the slide and magazine release. For example, the subcompact Glock 26 will accept magazines from both the full-size Glock 17 and the compact Glock 19, but the Glock 17 will not accept magazines from the smaller Glock 19 or the Glock 26. The magazines for the Glock 36, the Glock 42, and the Glock 43 are all unique; they cannot use magazines intended for another model, nor can their magazines be used in other models.

The Glock 17 has a fixed polymer combat-type sighting arrangement that consists of a ramped front sight and a notched rear sight with white contrast elements painted on for increased acquisition speed – a white dot on the front post and a rectangular border on the rear notch. The rear sight can be adjusted for windage (on certain models due to the windage sights not coming as factory default), as it has a degree of lateral movement in the dovetail it is mounted in. Three other factory rear sight configurations are available in addition to the standard 6.5 mm (0.26 in) height sight: a lower impact 6.1 mm (0.24 in) sight, and two higher impact versions – 6.9 mm (0.27 in) and 7.3 mm (0.29 in).^[60]

The Glock pistol accessories available from the factory include several devices for tactical illumination, such as a series of front rail-mounted "Glock tactical lights" featuring a white tactical light and an optional visible laser sight. An alternate version of the tactical light using an invisible infrared light and laser sight is available, designed to be used with an infrared night vision device. Another lighting accessory is an adapter to mount a flashlight onto the bottom of a magazine.

Polymer holsters in various configurations and matching magazine pouches are available. In addition, Glock produces optional triggers, recoil springs, slide stops, magazine release levers, and maritime spring cups. Maritime spring cups are designed to allow the pistol to be fired immediately after being submerged in water. They feature additional openings that allow liquids to flow and escape around them, offering enhanced reliability when water has penetrated into the firing pin assembly channel.

Magazine floor plates (or +2 baseplates), which expand the capacity of the standard magazines by two rounds are available for models chambered for the 9×19mm Parabellum, .45 GAP, .40 S&W, .357 SIG, and .380 ACP cartridges. In addition to the standard nonadjustable polymer sight line, three alternative sight lines are offered by Glock. These consist of steel, adjustable, and self-illuminating tritium night rear sights and factory steel and self-illuminating tritium contrast pointer steel front sights.

Following the introduction of the Glock 17, numerous variants and versions have been offered. Variants that differ in caliber, frame, and slide length are identified by different model numbers with the exception of the Glock 17L.

Glock pistols are made in five form factors, all modeled after the original full-sized Glock 17. "Standard" models are designed as full-sized duty firearms with a large magazine capacity. "Compact" models are slightly smaller with reduced magazine capacity and lighter weight, while maintaining a usable grip length. "Subcompact" models are designed for easier carry, and being lighter and shorter, are intended to be used with two fingers on the grip below the trigger guard, and lack an accessory rail like the larger, after generation two, Glock models. The .45 ACP and 10mm Auto models have bigger, wider slides and are slightly larger than the smaller-chambered pistols and are available in the subcompact models Glock 29 (10mm) and Glock 30 (.45 ACP). Glock produces five models of single-stack "Slimline" subcompact pistols, the Glock 36 in .45 ACP, the Glock 42 in .380 ACP, and the Glock 43, 43x, and 48 in 9×19mm. The 43x and the 48 have longer grips that allow for a full three-finger hold and a 10 round capacity. "Competition" versions have longer barrels and slides, adjustable sights, an extended slide and magazine release.

Beginning in 2007, Glock introduced several "Short Frame" models designated by the suffix "SF". The short frame was originally designed to compete in the now cancelled U.S. military Joint Combat Pistol trials for a new .45 ACP pistol to replace the M9 pistol. Glock's entry featured an optional ambidextrous magazine release and MIL-STD-1913 rail along with a reduction in the size of the backstrap. The Glock 21SF is currently available in three versions: one with a Picatinny rail and ambidextrous magazine release and two with a Universal Glock rail available with or without the ambidextrous magazine release. Current 10mm and .45 ACP Glock magazines are manufactured with ambidextrous magazine release cutouts. As of January 2009, the Glock 20, 21, 29, and 30 were offered in short-framed variations. These models incorporate a 2.5 mm (0.098 in) reduction in trigger reach, and full-sized models feature a 4 mm (0.16 in) reduction in heel depth, which corresponds to an overall reduction in length for those models.^[61][62][63]

Glock pistols chambered for the .45 ACP (and the .45 GAP) feature octagonal polygonal rifling rather than the hexagonal shaped bores used for models in most other chamberings.^[81] Octagonal rifling provides a better gas seal in relatively large diameter rifled bores, since an octagon resembles a circle more closely than a hexagon.^[55]

As is typical of pistols chambered in .40 S&W, each of the standard Glock models (22, 23, and 27) may be easily converted to the corresponding .357 SIG chambering (Glock 31, 32, and 33, respectively) simply by replacing the barrel. No other parts need to be replaced, as the .40 S&W magazines will feed the .357 SIG rounds.

The first two .380 ACP models are primarily intended for markets which prohibit civilian ownership of firearms chambered in military calibers such as 9×19mm Parabellum.^[89] Despite this they are legally prohibited from being sold to civilians in the United States due to being manufactured in Austria and not meeting the import restrictions based on its caliber,^[90] they are also prohibited from ownership in Canada due to not meeting minimum barrel length requirements for handguns.

Due to the relatively low bolt thrust of the .380 ACP cartridge, the locked-breech design of the Glock 19 and Glock 26 was minimally modified for the Glock 25 and Glock 28 to implement unlocked breech operation. It operates via straight blowback of the slide. This required modification of the locking surfaces on the barrel, as well as a redesign of the former locking block. Unusual for a blowback design, the barrel is not fixed to the frame. It moves rearward in recoil until it is tilted below the slide, similar to the standard locked-breech system. The reduced size and mass of the Glock 42 required return to the Glock-standard locked-breech design.

As is typical of pistols chambered in .357 SIG, each of the standard Glock models (31, 32, and 33) may be easily converted to the corresponding .40 S&W chambering (Glock 22, 23, and 27, respectively) simply by replacing the barrel. No other parts need to be replaced, as the .357 SIG magazines will feed the .40 S&W round.

Glock pistols chambered for the .45 GAP (and the .45 ACP) feature octagonal polygonal rifling rather than the hexagonal shaped bores used for models in most other chamberings.^[81] Octagonal rifling provides a better gas seal in relatively large diameter rifled bores, since an octagon will have shorter sides and shallower angles than a hexagon.^[55]

Aside from the original Austrian company, Glock pistols are manufactured by the Glock Inc. subsidiary division located in the United States. Those batches are nearly the same or identical compared to the Austrian-made ones, but they are marked as "USA", instead of "AUSTRIA", on the slide; and they have seven-digit serial numbers, instead of the Austrians' six. Glock 17 pistols are being assembled locally at army workshops of Uruguay to fulfill the needs of the national military services and law enforcement organizations.^[93]

The 205th Armory in Taiwan produces a copy of the Glock 19, named as the T97 pistol. The Taiwan-made Glocks were made to replace the Smith & Wesson Model 5906 used by the Taiwan police, but it ultimately did not enter service. Turkish company Akdal Arms produces a pistol named the Ghost TR01, which is heavily influenced by Glock pistols in its design.^[94]

Russian firms such as Skat,^[95] ORSIS^[96] and Izhmash^[97] assembles three models of Glock pistols locally: the Glock 17, 34, and 35.

There are three sidearms made by Iranian DIO's Shahid Kaveh Industry Complex which they call Ra'ad (has a safety selector, possibly an unlicensed copy of Glock 17), Glock 19 and Kaveh-17 (probably an improved Ra'ad, a variant of Glock 17S), which all of them are unlicensed clones of Glock pistols.^[98] It is not known if they could make their way to Iranian Military and replace the Browning Hi-Power, 1911 and SIG P226 pistols and they were possibly some prototypes and have never gone on mass production.^[99]

The Tatmadaw of Burma has adopted a clone of the Glock 17 known as the MA5 MK II.^[100] They're currently being manufactured and adopted for Myanma special forces units.^[101]

Glock pistols have been used in mass shootings including the 2007 Virginia Tech shooting, 2011 Norway attacks, 2012 Aurora shooting, 2012 Sandy Hook massacre, 2016 Orlando nightclub shooting, and the 2018 Pittsburgh synagogue shooting. Experts on gun policy, mass shootings, and defense training have cited factors such as reliability, ease of use and availability. The criminal use of these legally purchased weapons has led to calls for increased gun control in the United States.^{[196][197][198]}