Glock 21 vs Glock 19 Comparison

by Travis Pike

July 11, 2023



Glock’s black, blocky, and often Spartan guns are market dominators. Why? Lots of reasons. They work for one, are affordable, and often offer a very reliable platform to shooters. One of the big reasons why Glock has been successful is that they are fairly innovative. In 2023, it seems like they lag a bit behind, but that’s not a fair judgment since the rest of the market seems to only be catching up now. 

With innovation in mind, I wanted to talk about two of Glock’s old-school innovators, the Glock 19 and Glock 21 pistols. These two guns have a ton of history behind them and very dedicated fan bases. Glock has produced both guns for five generations, cementing their place in the brand’s history. They are also competitors in a variety of different ways. It’s crazy what two very different guns can have in common. 

Spec Comparison

Glock 21 Gen 5 Review

Glock 21 Gen 5

  • Final Grade : B+
Caliber .45 ACP
Action Striker
Capacity 13
Front Sight Fixed
Rear Sight Dovetail
Optics Ready MOS
Barrel Length 4.61 in
Weight (loaded) 38.8 oz
Frame Polymer
Slide Width 1.12 in
Grip Width 1.34 in
Overall Length 8.07 in
Height 5.51 in
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Glock 19 Gen 5 MOS Feature Image

Glock 19 Gen 5 MOS

  • Final Grade : A
Caliber 9mm
Action Striker
Capacity 15
Front Sight Fixed
Rear Sight Dovetail
Optics Ready MOS
Barrel Length 4.02 in
Weight (loaded) 30.16 oz
Frame Polymer
Slide Width 1.00 in
Grip Width 1.26 in
Overall Length 7.36 in
Height 4.99 in
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Why the Glock 21 vs. Glock 19?

Glock 21 vs Glock 19 Comparison

What these guns have in common are their somewhat revolutionary designs. Keep in mind these guns have been around for decades now, and when they premiered, they both did something different. The Glock 19 created the modern compact handgun. It delivered us a Goldilocks-sized portion of just right for duty, concealment, and home defense. It held the right amount of ammo and combined a somewhat easy-to-conceal design with an easy-to-shoot layout. 

The Glock 21 swung into the world, delivering a double dose of .45 ACP. Keep in mind before the Glock 21, most .45s were single-stack designs. There was the SIG P220, the M1911, the S&W 4506, and many more. Glock came in with the Glock 21 and delivered 13 rounds of 45 ACP in a double-stack magazine. That blew away most .45s on the market, except for some truly giant guns like the Mk23.  Read our full Glock 21 review to get a focused review on just the 21.

These guns were both innovators and continue to be popular among Glock fans. Popular enough to make it to a Gen 5 designation with all the advanced features present in Gen 5 pistols. Both guns also have MOS options for factory-ready optics. 

While they have a ton in common, they are also natural rivals, so let’s dive into it. 

The Main Difference – Caliber 

The first and likely most important difference to most shooters will be the caliber. The Glock 19 is chambered in the humble but extremely popular 9mm while the Glock 21 uses the .45 ACP cartridge made famous by the 1911. While size varies by a few millimeters in terms of projectiles, these are fairly different rounds. Both rounds remain popular, and I have watched cartridges like .40 S&W and 10mm come and go. 

Most .45 ACP is naturally subsonic, making it easier to suppress. Most 9mm rounds are supersonic, making it tougher to suppress. With that said, there are plenty of supersonic 45 ACP and subsonic 9mm loadings as well. 

The classic 9mm vs. 45 ACP debate has settled recently. As the gun industry learned that things like stopping power were a myth, the .45 ACP became a little less prevalent. 9mm loads also improved, which led to better projectile designs and velocity. 

What we began to see is the size difference didn’t matter much because 9mm projectiles could expand significantly as they hit the body. To be fair, that same technology has led to a bigger .45 ACP expansion as well. 

The smaller sized 9mm allows for a higher capacity. The compact Glock 19 can hold 15 rounds, whereas the full-sized Glock 21 can hold only 13 rounds. If we stepped the Glock 19 up to a full-sized magazine, we could get 17 rounds. That’s nearly 25% more ammo. 

Not to mention the Glock 19 can use the Glock 33-round magazines as well. The Glock 21 only has a factory 13-round magazine, but the aftermarket has provided some longer options. 

9mm delivers less recoil, which results in faster follow-up shots. The .45 ACP isn’t snappy, but its push-like recoil hits harder than the 9mms. A well-trained shooter will probably perform pretty evenly with either, but for an average Joe like me, the difference is noticeable. 

At the end of the day, the caliber debate will never really end amongst gun owners. However, the 9mm seems to be the best cartridge for a defensive firearm in 2023. 

Upgrades and Accessories for Glock 21

Glock OEM Gen 4 13 Round 45 ACP
  • Factory magazine
  • Fit: Glock 41, 21, 21SF, 30 & 30SF
  • Caliber: .45 ACP
  • Capacity: 13-Round
  • Finish: Black
  • Body Material: Polymer with Steel Insert
  • Base pad: Polymer
  • Does not fit Gen 1-3 G21 SF
Check Price
Ghost Minus Trigger Connector for Glock
  • drop in replacement
  • 3.5lb trigger
  • Fits all Glock Pistols (except 42 & 43)
Check Price
Safariland 6360 Mid-Ride Duty Holster
  • ALS (Automatic Locking System) secures weapon once holstered; simple straight up draw once ALS is deactivated by thumb while obtaining shooting grip
  • Includes paddle and belt loop attachments
  • Belt loop adjusts for cant and fits 1.5″ (38mm) to 1.75″ (45mm) belts
Check Price

Size Differences 

This ends up being both a battle of compact versus full size and 9mm vs. .45 ACP once more. Ultimately, the size difference between the two calibers creates a size difference in the guns. Let’s talk about the differences the caliber size creates. First, the slide for the Glock 21 is 1.12 inches wide, and the Glock 19’s slides is only 1 inch wide. 

Both guns use a double-stack magazine, but the Glock 21’s grip is 1.34 inches wide, and the Glock 19’s grip is 1.26 inches wide. Some criticism was directed towards the large frame of the Glock 21, leading to the release of the 21SF series, which reduces the overall grip size for an easier trigger reach. 

Another big factor comes with weight. Unloaded, the Glock 19 weighs 23.63 ounces, and the Glock 21 weighs 29.28 ounces. When you load the gun, the difference becomes even more significant. A loaded Glock 21 weighs 38.8 ounces, and a Glock 19 loaded weighs 30.16 ounces. That’s half a pound difference. 

Outside of caliber, we are looking at a full-sized gun versus a compact. Here is where we see some differences in length and height. The Glock 19 uses a 4.02-inch barrel, and the Glock 21 uses a full-length 4.61-inch barrel. This creates an overall length distance of 8.07 inches for the Glock 21 and 7.36 inches for the Glock 19. The Glock 21 is taller at 5.51 inches compared to the Glock 19’s 4.99 inches. 

The Glock 21’s longer slide does give you a longer sight radius, which makes the gun easier to shoot accurately. That’s beneficial for sure. Normally the weight difference could offer the Glock 21 an advantage n recoil. However, since it’s firing the heavier recoiling 45 ACP cartridge, it’s recoiling more than the lighter 9mm Glock 19. 

If you have big hands, you might find the Glock 19’s grip a bit short, but that’s not a problem with the Glock 21. This likely affects a small group of people, but as the possessor of 2XL-sized hands, I find it relevant. 

Upgrades and Accessories for Glock 19

Glock OEM Gen 5 15 Round 9mm
  • Impact-resistant polymer construction
  • Full-length steel insert
  • Numbered witness holes
  • Compatible with compact 9mm models
Check Price
Glock OEM Gen 5 17 Round 9mm
  • Impact-resistant polymer construction
  • Full-length steel reinforcement inserts
  • Numbered witness holes
  • Impact-resistant polymer follower
  • Compatible with most 9mm Glock models
Check Price
Glock OEM Gen 4/5 33 Round 9mm
  • Durable polymer construction
  • Full-length steel reinforcements
  • Numbered witness holes
  • Impact-resistant polymer follower
Check Price
Ghost Minus Trigger Connector for Glock
  • drop in replacement
  • 3.5lb trigger
  • Fits all Glock Pistols (except 42 & 43)
Check Price
Safariland 6304RDS ALS/SLS QLS Woodland Camo Holster
  • Light and Red Dot compatible
  • QLS attachment system
  • WOODLAND CAMO….its a vibe
Check Price

Purpose and Design 

When we begin considering what each gun is best used for, we see a stark difference between the two. 

With the Glock 19, we have a gun that’s trying to be pretty good at everything. It can work for concealed carry, home defense, and duty use. It’s not the best in any of those categories, but it can work. The gun offers an accessory rail, a somewhat compact size, plenty of ammo in the magazine, as well as options for more ammo and even optics. 

The Glock 21 comes in with its XL-sized design and is great as a duty or home defense handgun. In this role, the big gun shines with its long sight radius and full-sized design. It’s also a decent competition handgun and can compete with 9mm in most competitions to power factor. The Glock 21 and the standard .45 ACP round meets the necessary rating for major power factor. 

From a Practical Standpoint 

The Glock 19 is the more popular weapon because most people find it good enough for so many roles. With the Glock 19, you get more ammo, a lighter, smaller, and easier-to-conceal gun with less recoil. It’s easier to shoot and will fit the hands of most shooters. That popularity leads to a much larger aftermarket for everything from triggers to holsters. 

The Glock 21 offers you a big .45 ACP weapon with a double-stack magazine that’s not offered by most gun companies. If you want a good .45 ACP handgun, then the Glock 21 is going to be tough to beat if you are aiming for modern. Like most Glocks, there is a decent aftermarket for these pistols, but it’s one of the smaller aftermarkets. 

The good news is that you are getting a good gun either way. Glock famously makes fantastic pistols, and the 19 and 21 are equal when it comes to reliability, accuracy, and design. Glock makes excellent guns, and either option will well serve you. Hopefully, we’ve made the choice a little easier to make. 


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About Travis Pike

Travis is a former United States Marine Corps Infantryman and currently a firearms writer, instructor, and works in Emergency Management.

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