4 Common Glock 21 Problems You Must Know

Last Update:

Hey Shooters! Welcome to my Glock 21 Problems Blog.

After spending quality time with the Glock 21 out in the field, I’m here to share some insights. I’ve put it through its paces and run it hard, and I’ve stumbled upon a few issues you might want to know about.

I’ve also noticed some common problems like slide rattles, feeding issues, failure to fire, and magazine problems. 

I will break down each issue, tell you why it happens, and then give you the solution you need to keep your Glock 21 running smoothly. So, let’s dive right in and get that pistol back in tip-top shape.

Quick Table For Glock 21 Issues

Slide Rattle IssueUse specific tools to tighten the slide rails for a more stable rear slide.
Feeding IssuesSwitch ammo to more reliable options; Add a stronger Recoil Spring Assembly (RSA) and magazine spring; Loosen grip.
Failure To FirePerform a good cleaning and field stripping; “Break in” the stiff spring with a few hundred rounds.
Magazine ProblemsLeave the magazine pushed as far into the frame as it’ll go, covered with a thin fabric, overnight.

Top 4 Common Glock 21 Problems & their Fixes

1. Slide Rattle Issue

So, let’s talk about that slide rattle issue. While shooting, I noticed that the rear of the slide on my Glock 21 seemed a bit loose. 

Sure, the Glock can take a beating, but an unsafe slide? That’s not ideal. This isn’t just an annoyance; it can impact your accuracy, and that’s not something we want, right? Now, it turns out there are a few reasons why this happens. 

One is the slide-on-frame looseness, which means the slide and the frame aren’t fitting as snugly as they should. Sometimes, this is due to wide tolerances or poorly fitting parts that give that slide too much room to move side to side.

How To Fix

Alright, so what’s the quick fix for this? I spoke to some gunsmiths who deal with 1911s, and they advised using specific tools to tighten the slide rails. And guess what? It worked for me. 

You don’t have to be a pro to do this; it’s a straightforward procedure. Just ensure you’re taking proper safety precautions when messing with your firearm, okay? 

Tightening the slide rails can make a big difference and stabilize that wobbly rear slide, making your shooting experience much more reliable. So, if you’re running into this issue, this quick fix is worth trying.

2. Feeding Issues

Next on our list is the notorious “Failure to Feed” issue. Now, this one can be especially frustrating, trust me. 

Picture this: you’re out on the range, and every other bullet just refuses to cooperate. It’s a mess, whether it’s crashing nose-first into the magazine or getting stuck under the barrel’s ramp. I noticed this happening with several types of ammo, notably Winchester PDX1s, Federal HSTs, and Hornady Critical Duty. 

This isn’t just a random hiccup; it’s a pattern. There are a couple of usual suspects here. First, gripping the pistol too tightly seems to be a contributing factor. 

Second, the magazine spring might not be keeping up with the slide speed.

How To Fix

So, how did I tackle this issue? I made a few changes based on some solid advice. Swapping the ammo for Federal HSTs, Remington Golden Sabers, and Speer Gold Dots made a difference, as the G21 fed these reliably. 

On top of that, adding a stronger Recoil Spring Assembly (RSA) and a counterweight to the slide helped. I even changed out the magazine spring for a beefier one. And yes, loosening my overly rigid grip made a notable impact. 

Remember, it’s all about finding that perfect balance. You’ve got to keep the ammo within the gun’s design parameters or tweak those parameters for different bullet loads. 

3. Failure To Fire

Another issue I encountered with the Glock 21 was that it didn’t want to fire at times. When racking the slide, it felt like it was sticking back. 

This was particularly odd because it only happened when the trigger was not being engaged. Now, the Glock 21, especially the Gen 4 model, comes with a stiffer spring compared to other Glock models. 

This seemed to be the heart of the problem. It’s also worth noting that this issue seems more prevalent in the .45 models. 

I considered the possibility of a “break-in” phase, even though Glocks aren’t particularly known for needing one.

How To Fix

So, how did I get around this? First off, I gave the gun a good cleaning and field stripping. Then, I took it out for a shoot, running a few hundred rounds through it. 

The idea was to “break in” the stiff spring, so to speak. I also made sure to lubricate the Gen 4 spring well with high-quality oil before getting started. 

After that workout, the not-firing issue pretty much resolved itself. Some folks recommend switching to a lighter aftermarket spring if you find yourself in a bind, but I’d advise against it. 

Stick with the original and give it time to loosen up; it’ll likely serve you well.

4. Magazine Problems

Ah, the infamous magazine problems. If you’re like me, you’ve been through this too. Around the tenth round, the magazine decides it’s had enough and fails to feed. 

This isn’t just a minor inconvenience; it’s a significant issue when you rely on your firearm. The rounds seem to lean back, and they’re not staying parallel with the follower. 

Oh, and let’s not forget how the magazine juts out from the gun’s bottom by about a half to a full inch. This can be a pain, especially if you have a holster designed for a snug fit. 

Now, some Glock frames appear to be molded too tightly, preventing the magazine from dropping freely.

How To Fix

So, what to do? I decided to try a simple solution that seemed almost too easy to work, but guess what? It did the trick. First, remove the slide from the frame. 

Take a a thin piece of fabric and place it over the troublesome magazine. Push the magazine as far into the frame as it’ll go. Now, just let it sit there overnight. 

When I tried this, I found that the magazine was easier to manage the next day. It might take a little patience, but it’s a simple and effective way to tackle this issue.

Also See: Best Red Dot For Glock 21

Final Verdict

After spending considerable time testing out the Glock 21, it’s safe to say that while it isn’t without its issues, it’s certainly a reliable firearm. 

The thing is, no piece of machinery, however well-designed, is free from occasional hitches. And that’s precisely what we’ve got here: problems like slide rattle, feeding issues, failure to fire, and magazine problems. But let me tell you, these issues are more like speed bumps on an otherwise smooth road. 

With a bit of patience and some straightforward fixes, the Glock 21 performs admirably well.

So, go ahead and invest the time to iron out those kinks. You won’t regret it; this gun will serve you well.


What is the Glock 21 known for?

The Glock 21 is renowned for its combination of accuracy, light recoil, and high magazine capacity in a .45 Auto caliber.

What’s better Glock 19 or Glock 21?

Both have their merits, but the Glock 19 offers more versatility with magazine options, being able to use 17-, 19-, 24-, and 33-round magazines, whereas the Glock 21 is limited to 13 rounds.

What military uses Glock 21

The Glock 21 is increasingly used by U.S. Special Operations Forces, which handle a variety of specialized missions, from unconventional warfare to foreign internal defense.

Is a Glock 21 reliable?

Yes, the Glock 21 is a reliable and durable .45 caliber pistol with a high-capacity of 13+1, making it a dependable choice for various applications.

One Request?

I worked hard on this post to help the shooters community. it would help me a lot if you consider sharing it on social media network

BecauseSharing Is Caring..

Because Sharing Is Caring..

Photo of author


I'm Micheal, an avid shooter and hunting enthusiast from Texas. I'm a recreational shooter who loves to spend time at the range and enjoy learning about new firearms and gears. I love to write about guns and share my passion for shooting with others.

Leave a Comment