Glock Generations Explained: What Fits Gen 3, Gen 4 and Gen 5

Gen 3, Gen 4 and Gen 5 GLOCK pistols look almost the same from a distance, but enough changed inside that a part listed only for "G19" can be the wrong part for your G19. This guide covers how to tell the generations apart, what carries across, what does not, and how to confirm fit before you order.

How to identify your generation

Gen 3

Gen 3 frames have finger grooves on the front of the grip, a thumb rest on the grip panels and an accessory rail on the dust cover. The grip has no interchangeable backstraps, and the slide carries no generation marking.

Gen 4

GLOCK lists four headline Gen4 features: a modular backstrap system, an enlarged reversible magazine catch, a dual recoil spring assembly and a Rough Textured Frame (RTF). Medium and large backstraps are included and swap with a single pin. Gen4 pistols keep the finger grooves and were the first with the generation marked on the slide.

Gen 5

GLOCK says the Gen5 pistols have more than 20 design changes from Gen4. The ones you can see or feel:

• No finger grooves on the front of the grip.
• Ambidextrous slide stop lever, with a lever on both sides of the frame.
• Flared magwell at the bottom of the grip.
• nDLC finish.
• GLOCK Marksman Barrel (GMB), which GLOCK describes as having more aggressive polygonal rifling, a target-style crown and tighter chamber specifications.
• Interchangeable backstraps, plus a beavertail option.

Gen5 slides are marked with the generation on the left side. Crossover models such as the G19X and G45 are listed alongside Gen5 models in many factory parts listings.

What changes between generations

Recoil spring assemblies

This is the clearest split. Gen 3 pistols use a single-spring assembly, such as the factory compact assembly marked 5593-1 that is listed for the Gen 1 to 3 G19, G23, G32 and related models. Gen 4 brought a dual spring assembly, which GLOCK says reduces felt recoil and increases service life.

Gen 4 and Gen 5 assemblies are not automatically the same part. The factory G19 Gen4 assembly is marked 0-4-4, while the G19 Gen5 assembly, which also fits the G19X, G45 and G45 MOS, is marked 1-7-1. Order by model and generation.

Trigger, trigger bar and housing

GLOCK lists separate factory triggers with trigger bars for each generation. The smooth Gen 1 to 3 standard-frame trigger is marked with one dot, the Gen4 standard-frame trigger is marked 3600-1, and the Gen5 and crossover trigger for 9mm and .40 is marked 39701.

Gen 5 also changed the trigger mechanism housing. GLOCK credits changes to the firing pin safety and trigger spring with better housing durability, a smoother pull and improved reset. Brownells describes the Gen5 housing as eliminating the connector spring, with the trigger return spring moved inside the housing. Aftermarket triggers follow the same split: Apex sells one Action Enhancement trigger for Gen 3 and 4 and a separate Gen 5 version that it states does not function in Gen 3 or Gen 4 models.

Slide stop lever

The Gen5 ambidextrous slide stop lever is a Gen5 part. The factory 9mm and .40 version, marked 47246, is listed for Gen5 and crossover models and excludes Slimline, Competition and Long Slide frames. It is not listed for Gen 3 or Gen 4 pistols.

Locking block

Some locking blocks do cross generations. One factory compact locking block is listed for the G19, G19X, G23, G32, G38 and G45, covering Gen 3 pistols made in 2013 and later, Gen 4 and Gen 5. An older Gen 3 may need a different block, so check the listing.

Firing pin and firing pin safety

Gen 5 uses its own firing pin parts. The 9mm firing pin for the Gen 1 to 4 G17, G19, G26 and G34 is listed as excluding all Gen5 models and the G19X and G45. GLOCK sells a separate Gen5 9mm firing pin assembly. The firing pin safety follows the same pattern: the Gen 1 to 4 part excludes Gen5 and crossover models, and the Gen5 9mm part, marked with three dashes, is listed for 9mm Gen5 models only.

Magazines

Gen 4 and Gen 5 magazines have notches on both sides of the magazine body so the reversible magazine catch works from either side. GLOCK's Gen4 launch material said earlier magazines would continue to work in Gen4 pistols as long as the magazine catch was left in its original position. If you reverse the catch for left-handed use, you need magazines with the extra notch.

Whether Gen5 magazines, with their orange followers and extended floorplates, are suited to older pistols could not be confirmed from GLOCK's own pages, and retailer sources disagree. Check the fitment line on the specific magazine listing.

Slides and frames

Do not assume a slide from one generation fits a frame from another. ZEV, for example, sells its G19 slides in separate Gen 1 to 3, Gen 4 and Gen 5 versions, and states that its Gen 3 conversion slides will not work on Gen4 or Gen5 frames. Treat slides and frames as generation-specific unless the maker lists your exact frame.

Fit table

How to check fit before you order

1. Confirm model and generation. Check the slide marking, then the grip. Finger grooves with no backstraps points to Gen 3. Finger grooves with backstraps and a reversible catch points to Gen 4. No finger grooves and an ambidextrous slide stop points to Gen 5.
2. Read the full fitment line. Look for the generation, and watch for exclusions such as Slimline, crossover, Competition or Long Slide.
3. Match the factory marking. Many GLOCK parts carry a marking, such as 0-4-4 or 1-7-1 on a recoil spring assembly. Compare it to the part you are replacing.
4. Treat Gen 5 as its own platform. For trigger parts, firing pin parts and the slide stop, assume Gen5 and crossover models need Gen5 parts unless the listing says otherwise.
5. Get it installed and checked. GLOCK and most parts makers recommend installation by a GLOCK certified armorer or qualified gunsmith. After any parts change, perform a function check with the pistol unloaded.

Shop

Browse factory and aftermarket GLOCK parts for Gen 3, Gen 4 and Gen 5 pistols, including triggers, connectors and guide rods and recoil springs. Each listing shows the models and generations it fits.