The company's founder, engineer Gaston Glock, had no experience with firearm 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. Glock introduced ferritic nitrocarburizing into the firearms industry as an anti-corrosion surface treatment for metal gun parts.
In 1980, the Austrian military announced that it would seek tenders for a new, modern duty pistol to replace their World War II-era Walther P38 handguns. The Austrian Ministry of Defence formulated a list of 17 criteria for the new generation service pistol:
- The design has to be self-loading.
- The pistol must fire the NATO-standard 9×19mm Parabellum round.
- The magazines would not require any means of assistance for loading.
- The magazines must have a minimum capacity of 8 rounds.
- All actions necessary to prepare the pistol for firing and any actions required after firing must be done single-handed, either right- or left-handed.
- The pistol must be absolutely secure against accidental discharge from shock, stroke and drops from a height of 2 meters onto a steel plate.
- Disassembly of the main parts for maintenance and reassembling must be possible without the use of any tools.
- Maintenance and cleaning of the pistol must be accomplished without the use of tools.
- The pistol's construction may not exceed 58 individual parts (equivalent of a P38).
- Gauges, measuring and precise testing devices must not be necessary for the long-term maintenance of the pistol.
- The manufacturer is required to provide the Ministry of Defence with a complete set of engineering drawings and exploded views. These must be supplied with all the relevant details for the production of the pistol.
- All components must be fully interchangeable between pistols.
- No more than 20 malfunctions are permitted during the first 10,000 rounds fired, not even minor jams that can be cleared without the use of any tools.
- After firing 15,000-rounds of standard ammunition, the pistol will be inspected for wear. The pistol will 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 rated at 2,520 bar (252 MPa; 36,500 psi).) The critical components must continue to function properly and be up to specifications, otherwise the pistol will be disqualified.
- When handled properly, under no circumstances may the user be endangered by case ejection.
- The muzzle energy must be at least 441.5 J when firing a 9mm S-round/P-08 Hirtenberger AG.
- Pistols scoring less than 70% of the total available points will not be considered for military use.
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. Within three months, Glock developed a working prototype that combined proven mechanisms and traits from previous pistol designs. The new weapon made extensive use of synthetic materials and modern manufacturing technologies in its design, making it a very cost-effective candidate. Several samples of the 9×19mm Glock 17 (so named because it was the 17th set of technical drawings of the company) were submitted for assessment trials in early 1982, and after passing all of the exhaustive endurance and abuse tests, Glock emerged as the winner with the Model 17.
The handgun was adopted into service with the Austrian military and police forces in 1982 as the P80 (Pistole 80), with an initial order for 25,000 guns. The Glock 17 outperformed 8 different pistols from five other established manufacturers (Heckler & Koch of Germany offered their P7M8, P7M13 and P9S, SIG Sauer of Germany 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).
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 ongoing 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. 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.
Shortly thereafter, the Glock 17 was accepted into service with the Norwegian, and Swedish Armed Forces, surpassing all prior NATO durability standards. As a result, the Glock 17 became a standard NATO-classified sidearm and was granted a NATO Stock Number (1005-25-133-6775).
By 1992, some 350,000 pistols had been sold in more than 45 countries, including 250,000 in the United States alone.
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. Other changes not dealing with frame and slide length are identified with suffixes, such as "C", which denotes compensated models. Minor options such as frame color, sights, and included accessories are identified by a separate model code on the box and do not appear anywhere on the firearm.
Glock pistols come in five form factors, all modeled after the original full-size Glock 17. "Standard" models are designed as full-size duty firearm 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 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 post generation two Glock models. .45 ACP and 10mm models have bigger, wider slides and are slightly larger than the smaller chambered pistols and are available in the sub-compact models Glock 29 (10mm) and Glock 30 (.45ACP). Glock produces a single-stack "Slimline" .45 ACP pistol, the Glock 36. "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 10 mm 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. This reduction in heel depth corresponds to an overall reduction in length for those models.
- The Glock 17 is the original 9×19mm Parabellum model, with a standard magazine capacity of 17 rounds. Several modified versions of the Glock 17 have been introduced.
- The Glock 17C was introduced in 1996 and incorporated slots cut in the barrel and slide to compensate for muzzle rise and recoil. Many other Glock pistols now come with this option, all with a "C" suffix on the slide.
- The Glock 17L was introduced in 1988 and incorporates a longer slide and extended barrel. Initially, the Glock 17L had three holes in the top of the barrel and a corresponding slot in the slide; however, later production pistols lack the holes in the barrel. The Glock 17L is manufactured in limited quantities.
- The Glock 17MB is a version with ambidextrous magazine catch. This model, along with the other MB variants, was discontinued upon the introduction of the fourth-generation models, which features a reversible magazine catch.
- The Glock 18, chambered in 9×19mm Parabellum, fitted with a detachable shoulder stock being fired in fully automatic mode
- The Glock 18 is a selective fire variant of the Glock 17, developed at the request of the Austrian counter-terrorist unit EKO Cobra. Originally produced in 1986, this machine pistol–class firearm has a lever-type fire-control selector switch, installed on the serrated portion of the rear left side of the slide. With the selector lever in the bottom position, the pistol will fire fully automatic, and with the selector lever in the top position, the pistol will fire semi-automatically. The firearm is typically used with an extended 33-round capacity magazine, although other magazines from the Glock 17 will function, with available capacities of 10, 17, or 19 rounds. Early Glock 18 models were ported to reduce muzzle rise during automatic fire. Another compensated variant was produced, known as the Glock 18C. It has a keyhole opening cut into the forward portion of the slide, similar to the opening on the Glock long-slide models, although the Glock 18 has a standard-length slide. The keyhole opening provides an area to allow the four, progressively larger (from back to front) compensator cuts machined into the barrel to vent the propellant gases upwards, affording more control over the rapid-firing machine pistol.
- The compensator cuts start about halfway back on the top of the barrel. The two rear cuts are narrower than the two front cuts. The slide is hollowed, or dished-out, in a rectangular pattern between the rear of the ejection port and the rear sight. The rate of fire in fully automatic mode is approximately 1,100–1,200 rounds per minute. Most of the other characteristics are equivalent to the Glock 17, although the slide, frame, and certain fire-control parts of the Glock 18 are not interchangeable with other Glock models.
- The Glock 19 is effectively a reduced-size Glock 17, called the "Compact" by the manufacturer. It was first produced in 1988, primarily for military and law enforcement. The Glock 19 has a barrel and pistol grip that are shorter by approximately 12 mm (0.5 in) compared to the Glock 17 and uses a magazine with a standard capacity of 15 rounds. The pistol is compatible with factory magazines from the Glock 17 and Glock 18, giving the Glock 19 available capacities of: 17 rounds (standard magazine with +2 extension), 10, 17, and 19 (standard Glock 17 magazine with +2), and the 31 (standard Glock 18 magazine with +2 removed) and 33 rounds of the Glock 18. To preserve the operational reliability of the short recoil system, the mass of the slide remains the same as in the Glock 17 from which it is derived. With the exception of the slide, frame, barrel, locking block, recoil spring, guide rod, and slide lock spring, all of the other components are interchangeable between the models 17 and 19.
- The Glock 26 is a 9×19mm "subcompact" variant designed for concealed carry and was introduced in 1995, mainly for the civilian market. It features a smaller frame compared to the Glock 19, with a pistol grip that supports only two fingers, a shorter barrel and slide, and a double-stack magazine with a standard capacity of 10 rounds. A factory magazine with a +2 extension gives a capacity of 12 rounds. In addition, factory magazines from the Glock 17, Glock 18, and Glock 19, with capacities of 15, 17, 19, 31 and 33 rounds, will function in the Glock 26. More than simply a "shortened" Glock 19, design of the subcompact Glock 26 required extensive rework of the frame, locking block, and spring assembly that features a dual recoil spring.
- The Glock 34 is a competition version of the Glock 17. It is similar to its predecessor, the Glock 17L, but with a slightly shorter slide and barrel, to meet the maximum size requirements for many sanctioned action pistol sporting events. It was developed and produced in 1998, and compared to the Glock 17, features a 21 mm (0.8 in) longer barrel and slide. It has an extended magazine release, extended slide stop lever, 20 N (4.5 lbf) trigger pull, and an adjustable rear sight. The sides at the front of the slide are slanted instead of squared. Further the top of the slide and parts of its inside are milled out, creating a conspicuous hole at the top designed to reduce front-end muzzle weight to better balance the pistol and reduce the overall weight of the slide.
- The Glock 43 is a "slimline" version of the subcompact Glock 26 that features an ultra-compact slide and frame. The Glock 43 is the first Glock pistol to be manufactured with a single-stack 9×19mm Parabellum magazine, having a standard capacity of 6 rounds and being unique to the model. Unlike other subcompact Glock pistols, the Glock 43 cannot use factory magazines from its larger relatives due to its single-stack magazine design.
- The Glock 20, introduced in 1991, was developed for the then-growing law enforcement and security forces market for the 10mm Auto. The pistol will handle both full-power as well as reduced "FBI" loads that have reduced muzzle velocity. Due to the longer cartridge and higher pressures, the pistol is slightly larger than the Glock 17, having an approximately 2.5 mm (0.1 in) greater width and 7 mm (0.3 in) greater length. Though many small parts interchange with the Glock 17, with a close to 50% parts commonality, the major assemblies are scaled-up and do not interchange. The standard magazine capacity of the Glock 20 is 15 rounds. In 2009, Glock announced they would offer a 152 mm (6.0 in) barrel as a drop-in option.
- The Glock 20SF is a version of the Glock 20 that utilizes the Short Frame (SF) which is based on the standard G20 frame (same width), but reduces the trigger reach from the back of the grip by 2.5 mm (0.098 in) and the heel of the pistol is shortened by 4 mm (0.16 in) so the trigger can be reached and operated better by users with relatively small hands.
- The Glock 29 is a 10mm Auto equivalent of the subcompact Glock 26 introduced in 1997 along with the Glock 30 (.45 ACP). The pistol features a 96 mm (3.8 in) barrel and a standard magazine capacity of 10 rounds. Like other subcompact Glock pistols, the Glock 29 will function with the factory magazines from its related full-size model, giving an optional capacity of 15 rounds.
- The Glock 29SF is a version of the Glock 29 that utilizes the Short Frame (SF) which is based on the standard G29 frame (same width), but reduces the trigger reach from the back of the grip by 2.5 mm (0.098 in).
- The Glock 40, introduced in 2015, is a 10mm Auto equivalent of the long slide Glock 17L. The Glock 40 is only made with the "Gen4" frame and "MOS" (Modular Optic System) configuration.
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. Octagonal rifling provides a better gas seal in relatively large diameter rifled bores, since an octagon resembles a circle more closely than a hexagon.
- The Glock 21 is a .45 ACP version of the Glock 20 designed primarily for the American market. Compared to the Glock 20 chambered in 10mm Auto, the slide of the Glock 21 is lighter to compensate for the lower-energy .45 ACP cartridge. The standard Glock 21 magazine is of the single-position-feed, staggered-column type with a capacity of 13 rounds.
- The Glock 21SF is a version of the Glock 21 that utilizes the Short Frame (SF) which is based on the standard G21 frame (same width), but reduces the trigger reach from the back of the grip by 2.5 mm (0.098 in) and the heel of the pistol is shortened by 4 mm (0.16 in) so the trigger can be reached and operated better by users with relatively small hands.
- The Glock 30 is a .45 ACP version of the subcompact Glock 29, with a standard magazine capacity of 10 rounds. The factory magazine from the Glock 21, with a capacity of 13 rounds, will function in the Glock 30.
- The Glock 30SF is a version of the Glock 30 that utilizes the Short Frame (SF) which is based on the standard G30 frame (same width), but reduces the trigger reach from the back of the grip by 2.5 mm (0.098 in). The G30SF utilizes the same standard double-stack .45ACP magazines as the G30 and G21.[non-primary source needed]
- The Glock 30S is a version of the Glock 30 that features a thin slide (same slide as the G36), a Short Frame (SF) and a double stack magazine. The magazine holds 10 rounds.
- The Glock 36 is a "slimline" version of the subcompact Glock 30 that features an ultra-compact slide and frame and is chambered for the .45 ACP cartridge. The Glock 36 is the first Glock pistol to be manufactured with a single-stack magazine, having a standard capacity of 6 rounds and being unique to the model. Unlike other subcompact Glock pistols, the Glock 36 cannot use factory magazines from its larger relatives due to its single-stack magazine design.
- The Glock 41 is a competition version of the Glock 21, much like what the G34 is in relation to the G17; it features a 5.3 inch barrel and an elongated slide to accommodate for it. The Glock 41 is only made with the "Gen4" frame.
- The Glock 22 is a .40 S&W version of the full-size Glock 17 introduced in 1990. The pistol uses a modified slide, frame, and barrel to account for the differences in size and power of the .40 S&W cartridge. The standard magazine capacity is 15 rounds.
- The Glock 23 is a .40 S&W version of the compact Glock 19. It is dimensionally identical to the Glock 19 but is slightly heavier and uses a modified slide, frame, .40 S&W barrel and a standard magazine capacity of 13 rounds. The factory 15-round magazine from the larger Glock 22 will function in the Glock 23.
- The Glock 24 is a .40 S&W long slide variant of the Glock 22, similar in concept to the Glock 17L. Additionally, a compensated ported-barrel version designated the 24C was also produced. The Glock 24 was introduced in 1994 and officially dropped from the company's regular product lineup upon the release of the Glock 34 and 35. However, Glock continues to make small batch runs of the Glock 24 and 24C (as well as the similarly sized Glock 17L) at irregular intervals to satisfy consumer demand built-up for factory-new units, as shown by the release into the marketplace of new production of these models during the spring of 2010 and summer of 2011.
- The Glock 27 is a .40 S&W version of the subcompact Glock 26, with a standard magazine capacity of 9 rounds. The factory magazines from the larger Glock 22 and 23 will function in the Glock 27, increasing capacity to 13 or 15 rounds. Spacers are available that fit on these larger-capacity magazines themselves; they have the effect of "extending" the magazine well of the pistol, thereby improving the ergonomic feel of the pistol when the longer magazines are inserted.
- The Glock 35 is a .40 S&W version of the competition Glock 34.
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 round.
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.
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.
- The Glock 25, introduced in 1995, is a blowback derivative of the compact (102 mm (4.0 in) barrel) Glock 19. The magazine capacity is 15 rounds. Standard fixed sight elevation is 6.9 mm, unlike the 6.5 mm elevation used for the 9×19mm models.
- The Glock 28, introduced in 1997, is a blowback derivative of the subcompact (87 mm (3.4 in) barrel) Glock 26. The standard magazine capacity is 10 rounds, but the 15-round Glock 25 magazine will function in the Glock 28. Standard fixed sight elevation is 6.9 mm, unlike the 6.5 mm elevation used for the 9×19mm Parabellum models.
- The Glock 42, introduced in 2014, is an all-new locked-breech "slimline" (83 mm (3.3 in) barrel) design. The single-stack magazine is unique to this model, with a capacity of six rounds. It is Glock's smallest model ever made and is manufactured in the USA, which unlike the Glock 25 and 28 allows domestic sales in that market. The Glock 42 introduced several significant design changes relative to all prior Glock models:
- Redesigned firing pin safety: Wider non-rotating firing pin safety.
- Slide stop lever coil spring: Coil spring eases assembly, changes order of assembly and disassembly, eliminates possibility of misaligning slide stop lever spring.
- Reconfigured trigger return spring
- The Glock 31 is a .357 SIG variant of the full-sized Glock 22. The standard magazine capacity of the Glock 31 is 15 rounds.
- The Glock 32 is a .357 SIG variant of the compact Glock 23. The standard magazine capacity of the Glock 32 is 13 rounds.
- The Glock 33 is a .357 SIG variant of the subcompact Glock 27. The standard magazine capacity of the Glock 33 is 9 rounds.
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. Octagonal rifling provides a better gas seal in relatively large diameter rifled bores, since an octagon resembles a circle more closely than a hexagon.
- The Glock 37 is a .45 GAP version of the Glock 17. It uses a wider, beveled slide, larger barrel, and different magazine, but is otherwise similar to the Glock 17. The Glock 37 first appeared in 2003. It was designed to offer ballistic performance comparable with the .45 ACP in the frame size of the Glock 17. The concern with the size of the Glock 20/21 has been addressed by the Glock 36, 21SF, and 30SF all of which featured reduced-size frames. The standard magazine capacity of the Glock 37 is 10 rounds.
- The Glock 38 is a .45 GAP version of the compact Glock 19. The standard magazine capacity of the Glock 38 is 8 rounds.
- The Glock 39 is a .45 GAP version of the subcompact Glock 26. The standard magazine capacity of the Glock 39 is 6 rounds.