The Glock G17 9 mm Luger pistol is considered by some to represent a milestone for modern combat handgun design. Before the Glock arrived on the market, the idea of using impact-resistant plastic to form a pistol frame was seen as not only impractical, but laughable. It’s been more than 30 years since Austria adopted the Glock for use by its armed forces, and just a little more than 27 years since the pistol began to be imported for sale on the U.S. market. Needless to say, no one is laughing now. Just as the M1911 and CZ-75 have inspired the design features in many other pistols, plenty of gun manufacturers, both large and small, are using the Glock as the inspiration for their own polymer-frame semi-automatic handguns.

Dozens of changes to the Glock platform have been introduced through the years, even though the pistol appears to have remained essentially the same to those who are unfamiliar with it. After all, you can have any color of Glock you want, as long as it’s black. Some changes were developed as functional improvements to the gun, while others fulfilled specific military or law enforcement contract requirements (the recently released G30S in .45 ACP is a good example of a contract-to-market model).

Glock is now offering the fourth generation of its landmark pistol design, and to understand what makes Gen4 pistols different, and in some aspects just the same, as previous versions, it’s helpful to take a look at what came before. Although it’s neither possible nor practical to list all of the various modifications here, a general overview can be derived by looking at the major changes between each of the generations.

From Generation 1 to Generation 3 (1982 - 2009)
The first Glock pistols, including the Standard-size G17 9 mm (1982) and the G18 Select Fire models (1987), were duty-size pistols intended for military applications. The two most notable features, and the most controversial at the time, were the use of a polymer frame and the Safe-Action trigger ignition system, which excluded the use of grip or thumb safeties.

The pistol had a square slide treated with the Tenifer process to give it a 64 Rockwell C hardness rating and a high level of corrosion resistance. The gray Tenifer slide was then treated with a matte-black Parkerized finish to match the polymer frame. The fixed combat-style sights were made of polymer, with a white dot front sight and a white outline rear sight. The guide rod used an uncaptured spring, the frame had a 360-degree, light-texture grip surface, and the polymer 17-round detachable-box magazines were only partially lined with metal. They did not drop free from the frame when the magazine release was pressed.

By 1988, Glock was ready to introduce the second generation with the release of the first Compact-size model, the G19 9 mm, and the first long-slide version, the G17L. During the Gen2 time period, Glock would also introduce models chambered in .40 S&W (G22 and G23), .45 ACP (G21) and 10 mm (G20). A .380 ACP version was also developed (G25), but it is not, as of yet, available in the United States because of BATFE importation restrictions.

There were two varieties of the Gen2 frame. The two-pin frame, utilizing a support pin for the trigger and one for the trigger assembly, was employed for the 9 mm models and the now discontinued G24 .40 S&W. The three-pin frame had an additional pin installed above the trigger pin to lend added support to the locking block in the larger caliber models. Other internal changes included rear rail support tabs, which were longer than those of the Gen1 pistols (and later versions), a captured spring guide rod assembly, and improvements to key components such as the firing pin, extractor and trigger bar.

The Gen2 grip was enhanced with molded-in serrations and checkering on the front and back straps, which is now considered to be the earliest version of the Rough Texture Frame (RFT1). Magazines were upgraded to include a full-length metal lining, they dropped free from the grip, and the springs, followers and baseplates were improved.

In 1996, Glock began the introduction of what can be collectively categorized as the Gen3 feature set. This was also the year that the first Subcompact Glocks were launched with the introduction of the G26 9 mm and the G27 .40 S&W. Also known as “Baby Glocks,” the smallest of the Glock pistols utilize an abbreviated double-stack magazine and a stubby dual-recoil spring assembly instead of the single captured spring assembly found in the larger models.

Gen3 features included checkered finger grooves added to the frontstrap, as well as the addition of scalloped thumb rests on both the left and right sides of the grip. A molded-in accessory rail was added to the Standard and Compact models to facilitate the use of pistol-mounted lights and laser sighting modules. The extractors were reshaped to act as visible and tactile loaded-chamber indicators.

During 2003, Glock marked another important milestone for the company with the introduction of the first pistol cartridge to bear the company’s name, the .45 GAP (Glock Automatic Pistol). The cartridge, with its accompanying pistols (G37, G38 and G39), was originally developed for American law enforcement agencies that wanted the stopping power of the .45 ACP cartridge in a pistol with the slim grip and slide profile of Glock’s 9 mm offerings. Although the .45 GAP cartridge has proven to be a reliable and accurate round, it has yet to catch on as a mainstream defensive cartridge.

Beginning in 2007, Glock introduced the Short-Frame (SF) version of the G21, called the G21SF, followed by SF versions of other large-frame pistols including the G20, G29, and G30. Originally intended to compete in certain military contract trials, the SF models have a 0.098-inch reduction in trigger reach, and full-size models feature a 0.16-inch reduction in backstrap depth. The result is a grip frame that’s a more comfortable fit for shooters with smaller hands. The year also the marked the company’s milestone of selling more than 5 million pistols worldwide.

A few of the Gen3 pistols manufactured, prior to the introduction of the Gen4 models, featured the second generation of the Rough Texture Frame (RTF2). It consisted of small raised dots covering the sides and backstrap, closely mimicking a popular aftermarket modification of applying heavy-grit grip tape to the frame to provide better traction. They also had curved, gill-like slide serrations instead of straight cuts. Neither of those features survived into the fourth generation.

Generation 4 (2010 - Present)
In 2010, the Gen4 pistols arrived on the scene with nine models sporting the freshly introduced design updates. As of this writing, all but one of the pistols sold in the United States (G36 Slim Frame) are available with the latest features. The primary internal change of this iteration was a move from a single-spring recoil assembly to a new dual-spring assembly used in not only the Subcompact models as before, but in the Compact and Standard size pistols as well.

The rest of the Gen4 changes are primarily cosmetic in nature and occur on the frame. The magazine release has been enlarged from 0.20 inches to 0.50 inches in length. The release can also be relocated to the other side of the frame for left-handed shooters. Although Gen3 magazines can be used with a factory configured Gen4 magazine release, only the Gen4 magazines have an additional indentation required to accommodate the shift of the magazine release from the left to the right side. The grip features the latest rough texture design (RTF3) that consists of small, raised, blunted pyramids that replace the serrations and checkering found on the Gen3 models.

One more key change to the frame is the addition of an interchangeable backstrap system. Two backstraps and an installation tool are provided with new Gen4 pistols. The standard frame, with no backstrap installed, provides a grip profile like that of the SF models. Installing the thinner back strap returns the grip size to that of a standard Gen3 model, while installing the thicker backstrap adds an extra 0.08 inches of grip circumference for shooters with larger hands. Regardless of how the grip is configured, the grip angle remains the same.

With more than three years on the market now, how has the Gen4 pistol faired? Some Glock customers reacted to the Gen4 configuration changes much like Coca-Cola fans did when the drink company introduced New Coke in 1985. In other words, they were not impressed because they liked the pistol just the way it was. Those who liked the Gen3 grip saw no need for the added backstraps. During the 2010 to 2011 production run, a few of the new recoil assemblies suffered from reliability issues with certain varieties of ammunition, which further fanned the flames of some shooters’ discontent. In truth, less than 2 percent of the pistols constructed during the initial run exhibited reliability issues, and Glock quickly launched a voluntary spring-swap program for anyone who felt the part needed to be replaced.