Operating mechanism of The Glock 17 is a 9mm short recoil-operated locked breech semi-automatic pistol that uses a modified Browning cam-lock system adapted from the Hi-Power pistol

The Glock was modernized several times throughout its production history. In 1991 a modified version of the recoil spring and recoil spring tube was introduced that is now a single integrated recoil spring assembly that does not disassemble. Additionally the magazine was slightly modified (the magazine floorplate was changed and the follower spring was fitted with a resistance insert at its base) and the trigger pull was increased (optionally).

A mid-life upgrade to the Glock series involved the frame's grip, which received checkering on the front strap and serrations to the rear (these pistols are sometimes called the "generation 2" models). To meet ATF regulations, a steel plate with a stamped serial number has been embedded into the dust cover in front of the trigger guard. In the late 1990s the pistol's frame was further modified with a Universal Glock rail (used to mount laser sights and tactical flashlights), thumb rests on both sides of the frame and finger grooves on the front strap of the pistol grip ("generation 3" upgrade). The extractor has also been changed twice and the locking block was enlarged along with the addition of another pin
The Glock 17 is a 9mm short recoil-operated locked breech semi-automatic pistol that uses a modified Browning cam-lock system adapted from the Hi-Power pistol.[12] The firearm's locking mechanism utilizes 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 approximately 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