The company's founder, 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. Glock introduced ferritic nitrocarburizing into the firearms industry as an anticorrosion surface treatment for metal gun parts.
A "first-generation" Glock 17 with the slide locked back displaying its vertical barrel tilt
A "second-generation" Glock 17, identified by the checkering on the front and rear straps of the pistol grip and trigger guard
A "third-generation" Glock 17C, identified by the addition of an extra cross pin above the trigger, a reshaped extractor that serves as a loaded chamber indicator, and an accessory rail
A "fourth-generation" Glock 17, identified by an enlarged magazine release catch, modified rough texture frame grip checkering, interchangeable backstraps, and a "Gen4" rollmark on the slide
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. 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. 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).
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. 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) 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.
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 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).
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. 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.
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.
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.
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.
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. 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.
Comparison of "third-" (left) and "fourth-generation" (right) Glock 19 grip frames
Glock 17 Gen4 as issued by the British Armed Forces under the L131A1 General Service Pistol designation
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 Parabellum 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.
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.
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. 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.
2011 recoil spring assembly exchange program
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.
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. The solicitation specifications deviated from the specifications of Glock fourth-generation models.
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. 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".
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.
"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.