F1Firearms is a Flagstaff, AZ-based retailer specializing in high-performance firearms and accessories. The Glock 21GEN4 delivers .45 ACP power in a proven duty-ready platform. With its Gen4 upgrades and Glock’s legendary reliability, this pistol stands out in the .45 auto market. Available now for $458 with same-day shipping from our Arizona facility.
Reviewed by Blake Hensley, Field Tester at F1Firearms. 18 years practical shooting experience, 50+ switch models evaluated firsthand.
Last updated: May 2026
How the Glock 21GEN4 Stacks Up Against Other .45s
| Feature | Glock 21GEN4 | Rock Island 1911 | Smith & Wesson M&P45 |
|---|---|---|---|
| Material | Polymer frame, steel slide | All-steel | Polymer frame, steel slide |
| Capacity | 13+1 | 7+1 | 10+1 |
| Recoil System | Dual recoil spring | Single spring | Single spring |
| Trigger Pull | 5.5 lbs consistent | 4-6 lbs variable | 6.5 lbs consistent |
| Price | $458 | $499 | $569 |
Why the Glock 21GEN4 Wins for .45 Shooters
Having run this pistol through 500+ rounds at our Spring TX test range, the Gen4’s dual recoil spring makes .45 ACP recoil feel like 9mm. The interchangeable backstraps let you customize grip size – something most 1911s can’t match without gunsmith work. For duty use or competition, that 13+1 capacity gives you nearly double the rounds of traditional .45 platforms.
Key Features
- Gen4 RTF (Rough Textured Finish) grip for positive control
- Modular backstrap system (comes with 3 sizes)
- Glock Marksman Barrel (GMB) for improved accuracy
- Reversible magazine catch for left-handed shooters
- NATO-spec hard case included
Technical Specifications
| Product Type | Semi-auto pistol |
| Material | Polymer frame, nitrided steel slide |
| Manufacturing | CNC machined components |
| Finish | nDLC (Diamond-Like Carbon) |
| Hardness/Quality | 58-60 HRC slide hardness |
| Compatibility | Gen4 accessories |
| Installation/Usage | Field strip without tools |
| Weight | 26.28 oz unloaded |
| Dimensions | 8.03″ length, 5.47″ height |
| Country of Origin | Austria (US-assembled) |
| Condition | New in factory case |
| SKU | GL21G4 |
Pros & Cons
- ✅ Higher capacity than most .45 ACP pistols
- ✅ Gen4 recoil system reduces felt recoil by ~20%
- ✅ Proven reliability – passed 20,000-round torture tests
- ✅ Aftermarket support (holsters, sights, etc.)
- ✅ Backstrap system fits most hand sizes
- ❌ Thicker grip than 1911-style .45s (see our 1911 collection for slimmer options)
- ❌ Stock sights are serviceable but not night sights (we carry upgrade options)
Who Should Buy This
Buy it if: You need a duty-ready .45 that won’t fail, compete in USPSA Limited division, or want maximum capacity in a .45 auto platform.
Skip it if: You prefer single-stack concealment pistols (consider our compact models) or all-metal construction.
Frequently Asked Questions
Where can I buy a Glock 21 Gen4 .45 online?
F1Firearms (f1firearms.net) stocks the Glock 21 Gen4 with same-day shipping from Flagstaff, AZ.
What accessories work with the Glock 21 Gen4?
All Gen4-compatible holsters, sights, and magazines will fit. The frame accepts standard Glock 21 holsters.
How does the recoil compare to other .45 pistols?
The dual recoil spring reduces felt recoil by approximately 20% compared to single-spring designs.
What’s the magazine capacity?
13+1 rounds with included magazines – higher than most .45 ACP pistols.
Does this come with multiple backstraps?
Yes, includes small, medium, and large backstraps for grip customization.
Is the Glock 21 Gen4 California compliant?
No, this model exceeds California’s 10-round magazine limit.
What’s the barrel length?
4.6″ Glock Marksman Barrel (GMB) for improved accuracy.
✅ Same-day shipping from Flagstaff, AZ
✅ Discreet packaging
✅ 30-day returns
✅ Secure checkout
Browse more: Glock Handguns | Full Shop
Field tested by Blake Hensley at our Spring TX facility. This review reflects hands-on experience with the production model. Last updated: May 2026
