Glock 21 Gen4
- Category
- Pistol
- Barrel
- 117 mm
- Weight, empty
- 745 g
- Introduced
- 2012
About
What it is, and why it matters
The Glock 21 Gen4 is the fourth-generation full-size .45 ACP service pistol from Glock, delivering the stopping power of the .45 Auto round in a polymer-framed, striker-fired platform with a standard 13-round magazine capacity. The Glock 21 was originally introduced in 1990 as Glock's answer to American demand for a .45 ACP pistol, built on a modified Glock 20 (10mm Auto) frame to accommodate the wider .45 cartridge. The Gen4 variant, released in 2012, introduced the modular backstrap system with three interchangeable grip sizes, a dual recoil spring assembly with steel support for reduced felt recoil and extended service life, an enlarged reversible magazine catch, and a more aggressive rough-textured frame. Its octagonal polygonal rifled barrel provides improved accuracy and higher muzzle velocity compared to conventional land-and-groove barrels, while the Safe Action trigger system with three independent passive safeties ensures reliable and safe operation. The Glock 21 remains popular with law enforcement agencies and civilian shooters who prefer the proven .45 ACP cartridge in a high-capacity, lightweight, and reliable modern handgun.
The Glock 21 was Glock's first .45 ACP pistol, introduced in 1990 alongside the Glock 20 (10mm Auto). There was never a Gen1 Glock 21 -- the model postdates the Gen1 era entirely, making all original 1990 examples Gen2 pistols from the start.
The Glock 21 was the first .45 ACP pistol ever produced by Glock, introduced in 1990 alongside the Glock 20 (10mm Auto). Notably, there was no Gen1 Glock 21 -- all original 1990 models were Gen2 pistols, as the Gen1 era (1982-1989) predated the model's existence. The Gen4 dual recoil spring assembly replaced the Gen3's single captive spring, reducing felt recoil by approximately 20% and extending the spring's service life. Weight with empty magazine inserted is 830g. The slide width is 28.5mm (narrower than the 34mm overall frame width). Standard magazine capacity is 13 rounds with optional 10-round magazines available. The Gen4's modular backstrap system includes standard, small, and large grip inserts. The Glock 21 Gen4 has been superseded by the Gen5 MOS variant which adds the Glock Marksman Barrel, nDLC finish, flared magazine well, and optics-ready slide cuts.
Specification
Everything measured
IdentityWhat it is, who built it and when.
- Manufacturer
- Glock Ges.m.b.H.
- Category
- Pistol
- Country
- Austria
- Status
- In production
- Produced
- 2012
DimensionsAs issued, without a magazine or an optic.
- Barrel
- 117 mm
- Overall length
- 205 mm
- Height
- 140 mm
- Width
- 34 mm
- Sight radius
- 172 mm
- Weight, empty
- 745 g
- Weight, loaded
- 1.10 kg
ActionHow it cycles, what trips it, and what feeds it.
- Action
- Short recoil
- Firing mechanism
- Striker fired
- Trigger
- Safe action
- Trigger pull
- 28.0 N
- Capacity
- 13
- Magazine
- Detachable box
MaterialsEach swatch is the material itself, not a colour chosen to stand for it.
- Frame
- Polymer
- Slide
- Steel
- Barrel
- Steel
- Finish
- Gas nitride
BallisticsFrom the service cartridge, not a handload.
- Muzzle velocity
- 253 m/s
- Muzzle energy
- 477 J
- Effective range
- 50 m
- Maximum range
- 1500 m
Trajectory
What the round does downrange
Solved from the muzzle figures and the bullet. The dashed rule is the effective range on the record, and the crosses are the steps the solver returned.
Features
What it has
What the record lists as fitted, drawn from the catalogue.
Modular backstrap system
Reversible mag release
Dual recoil spring
Accessory rail
Rough textured frame
Finger grooves
Standing
How it compares
Each figure against the firearms of the same type and cartridge that record it, or of the same type where that cartridge has too few. Positions are read to the nearest tenth.
| Measurement | This firearm | Median | Position |
|---|---|---|---|
| Empty weightAmong 128 .45 ACP pistols | 745 g | 1.04 kg | Lighter than about 80% |
| Overall lengthAmong 129 .45 ACP pistols | 205 mm | 215 mm | Shorter than about 60% |
| Barrel lengthAmong 129 .45 ACP pistols | 117 mm | 117 mm | Near the median |
| Magazine capacityAmong 129 .45 ACP pistols | 13 | 8 | Holds more rounds than about 90% |
Answers
Questions about the Glock 21 Gen4
How much does the Glock 21 Gen4 weigh?
The Glock 21 Gen4 weighs 745 g (1.64 lb) empty and 1.10 kg (2.43 lb) loaded.
What caliber is the Glock 21 Gen4?
The Glock 21 Gen4 is chambered in .45 ACP.
How many rounds does the Glock 21 Gen4 hold?
The Glock 21 Gen4 holds 13 rounds, fed from a detachable box magazine.
How long is the Glock 21 Gen4?
The Glock 21 Gen4 is 205 mm (8.07 in) long overall, with a 117 mm (4.61 in) barrel.
Who makes the Glock 21 Gen4?
The Glock 21 Gen4 is made by Glock Ges.m.b.H. (Austria). It was designed by Gaston Glock.
When was the Glock 21 Gen4 introduced?
The Glock 21 Gen4 was introduced in 2012.
How does the Glock 21 Gen4 operate?
The Glock 21 Gen4 uses a short recoil action, and its firing mechanism is striker fired.
Compatibility
Which parts fit this firearm
Studio
Every part that mounts on this, resolved
Not a list the maker typed out: the answer comes from the mounts this firearm exposes and the interface each part needs, so it stays right when either one changes.
- Every part that mounts on any firearm in the catalogue
- Interface standards, platforms and fit overrides
- The same answers through the API and the MCP server
Requires a signed-in GunSpec account on the Studio plan. The answer is computed per part, so it is not part of the public record.
Provenance
What the record holds
Every figure above was taken from one of these pages. The confidence reflects how much of the record came from a page a claim can be checked against.
In service
- Hellenic Armed Forces
- Greece
- United States Special Operations Command
- United States
- Various U.S. Law Enforcement Agencies
- United States
Provenance
Confidence in this record
90%
Stockists
Where to buy
Offers link straight to the shop. GunSpec never takes the order.
No shop has listed this firearm yet
Stock and prices come from the shops themselves. If you sell this firearm, you can list it and it appears here.
List a firearmMCP
Ask an assistant about it
The same record, reached the way a person asks for it rather than the way a program does.
Ask GunSpec
Works with
Point an MCP client at GunSpec and it answers from the catalogue rather than from memory. A free key covers the read tools.
API
The call that returns this record
The same fields, in the same units, from the same endpoint the page reads.
curl --request GET \ --url 'https://api.gunspec.io/v1/firearms/glock-21-gen4' \ --header 'X-API-Key: your_key'{ "id": "glock-21-gen4", "name": "Glock 21 Gen4", "manufacturer": { "id": "glock", "name": "Glock Ges.m.b.H.", "countryCode": "AT", "foundedYear": 1963, "website": "https://www.glock.com", "logoUrl": null, "description": null, "status": null, "defunctYear": null, "stateOwned": null, "makesFirearms": null, "parentId": null, "predecessorId": null, "createdAt": "2026-02-11 23:44:38", "updatedAt": "2026-02-18 03:43:49", "version": "3082b5f3edc3e54ca4f0993c68dba8c456b4f86e8759e3310ef604da566477d6" }, "category": { "id": "pistol", "name": "Pistol", "description": "Handguns designed to be fired with one or two hands" }, "country_of_origin": "AT", "year_introduced": 2012, "barrel_length_mm": 117, "weight_empty_g": 745, "action_type": "short_recoil"}