Glock 21 Gen 4 Problems Revealed: Expert Fixes You Need

The Glock 21 Gen 4 is a remarkable specimen when delving into firearms.

The shooters encounter several Glock 21 Gen 4 problems that impact their experience with this firearm.

User reviews highlight common concerns such as frame malfunctions, failure to feed, rattling sounds, and inconsistent firing. 

The slide mechanism and magazine functionality also contribute to the overall performance of the Glock 21 Gen 4. 

Despite its reputation for reliability, the Glock 21 Gen 4’s grip design and surface area may only suit some shots, leading to discomfort and potential bending under pressure. 

Moreover, the interaction between the bullet and the feeding mechanism can result in occasional misfeeds and failures to fire, detracting from the gun’s effectiveness in critical situations.

Exploring alternative magazine options, examining the frame for structural issues, and fine-tuning the feeding mechanism can mitigate common malfunctions. 

Enhancing the grip ergonomics and optimizing the surface area can improve comfort and control during shooting sessions. 

Shooter feedback and user reviews are crucial in identifying failure patterns and implementing effective fixes to enhance the Glock 21 Gen 4’s reliability and performance.

Few Words For GLOCK 21 GEN 4

Gun experts scrutinize internal components like springs and triggers in firearms such as the Glock 21 Gen 4. 

Despite care, users may face jammed guns or failures to fire. Disassembly offers insight into the gun’s mechanics, ensuring intact parts. 

A thorough cleansing is vital before reassembly, guaranteeing readiness for subsequent shots.

For troubleshooting similar issues, explore solutions to Glock 20 Gen 4 Problems.

Regular checkups supplement Glock’s warranty, ensuring longevity and reliability.

Problems & Solutions at a Glance

6 ProblemsWith Their Quick Solutions
Bullet to FaceReplacing the ejector of the Gen 4 with the one from a 40-cal Glock can fix it.
Failure to Feed IssueEnhanced RSA, Slide/Barrel Counterweight, Stronger Magazine Spring.
Magazine IssuesRemove slide, cover magazine with thin clothing.
Slide Rattle ProblemUse tools for tightening slide rails that many 1911 gunsmiths are familiar with.
Not Firing IssuesClean, disassemble, shoot; Glocks skip “break-in” phase.
Heavy Trigger PullUsing a Dremel can lighten trigger pull and aid reassembly.
Glock 21 Gen 4 Problems

Glock 21 Gen 4 Problems With Their Practical Solutions

1. Bullet to Face Problem:

A concerning issue plaguing Glock 21 Gen 4 users is the occurrence of a bullet hitting the face during shooting sessions. This unexpected event can lead to injuries ranging from the forehead to the neck and shoulders.

The problem is observed across various ammunition types, including 230gr ball rounds from manufacturers like Winchester, Monarch, and Federal.

Users have reported that brass and steel casings are involved in this Gen 4 problem.

The root cause seems to be malfunctioning ejectors and extractors, which fail to manage the case properly upon ejection, resulting in bullets hitting the breech face unexpectedly.


Addressing the issue of bullets unexpectedly hitting the face with Glock 21 Gen 4 pistols requires a meticulous approach. Upgrading specific components can significantly mitigate this problem.

One effective solution involves installing a custom breach face cut to ensure smoother ejection of spent casings.

Replacing the factory ejector with a sturdier alternative, such as one designed for the Gen 5 or 40-cal Glock models, can enhance reliability.

Moreover, upgrading springs within the pistol’s mechanism, particularly those related to the extractor, can provide more consistent ejection patterns.

Opting for a high-quality stainless or Lone Wolf extractor can withstand the stresses of hotter ammo, reducing the likelihood of malfunctions related to case ejection.

2. Failure to Feed Issue:

Experiencing failure-to-feed (FTF) problems with Glock 21 Gen 4 pistols can be frustrating and potentially hazardous. Certain ammunition types, such as Winchester PDX1s, Federal HSTs, and Hornady Critical Duty, may often result in common FTF occurrences.

These issues manifest as bullets crashing or nose-diving into the barrel’s ramp, causing the magazines to become stuck.

Several factors contribute to this issue, including rigid hand-loading techniques and tight magazine springs, which may impede proper ammunition feeding.

Moreover, the slide speed can also affect the pistol’s ability to feed rounds smoothly.


Addressing the failure to feed (FTF) problem in Glock 21 Gen 4 pistols demands a thorough understanding of auto pistol mechanics.

Upgrading critical components like the Recoil Spring Assembly (RSA) and the magazine spring can enhance reliability.

Switching to ammunition brands like Federal HST, Remington Golden Sabers, and Speer Gold Dots may mitigate FTF occurrences, meeting specific design parameters for Glock pistols.

Optimizing the slide, barrel, and magazine interactions ensures smoother feeding cycles.

Modifying the pistol’s design to be stronger and more resilient to FTF issues is crucial. Adding weight or a counterweight stabilizes the slide for improved consistency.

Avoid holding the pistol too stiffly to prevent slide impedance when gripping it. Adjust grip parameters for smoother operation and choose ammunition loads within the recommended range to minimize FTF incidents.

3. Magazine Issues:

Magazine issues can disrupt feed consistency, affecting overall performance in Glock 21 Gen 4 handguns.

One common problem involves alignment discrepancies between the magazine and the feed mechanism. If the follower protrudes or the frames are too tightly molded, smooth feed cycles can impede.

Magazines failing to drop freely or align rounds properly within the bottom inch can lead to erratic feeding. 

Ensuring proper alignment of the magazine and the feed mechanism is crucial to prevent feed interruptions. Magazines should drop freely and align rounds parallel to the feed ramp for seamless operation.

Exploring potential reasons behind magazine issues involves assessing the alignment of internal components and inspecting for any protrusions that could hinder feeding.

It’s essential to address these issues promptly to maintain the reliability and performance of the Glock 21 Gen 4.


When addressing magazine issues in a Glock 21 Gen 4, it’s essential to consider various factors that might contribute to trouble with feeding and function. Sometimes, the solution lies in minor adjustments rather than major overhauls.

Firstly, ensure that the slide moves freely and isn’t obstructed by debris or misalignment. Secondly, the pistol’s frame should be examined to see if any irregularities could impede the magazine’s proper insertion and seating. 

Additionally, consider the clothing you wear while carrying the firearm; sometimes, thin materials like a t-shirt can inadvertently cause trouble by pushing the magazine too far or preventing it from thoroughly engaging.

Lastly, if you encounter persistent issues, leaving the magazine fully loaded overnight might be worthwhile to help settle the springs and alleviate any trouble with feeding.

These simple steps can often resolve trouble with Glock 21 Gen 4 magazines without requiring extensive modifications or replacements.

4. Slide Rattle Problem:

One of the common problems encountered with the Glock 21 Gen 4 is the slide rattle issue. This phenomenon occurs when the rear of the slide exhibits an unusual rattle or movement, especially when handling the firearm. Unlike the traditional snug fit in some handguns, Glocks is known for its wide tolerances and modular design. While this design philosophy contributes to their reliability, it can sometimes result in slight looseness or rattles. 

This rattle is often caused by improperly fitting parts or a sloppy fit between components. However, it’s essential to note that this rattle is usually cosmetic and does not affect the firearm’s performance or safety. Despite the initial concern it may cause, many Glock owners find that this slight rattle has no impact on the weapon’s functionality and is simply a characteristic of its design.


Addressing the slide rattle issue in the Glock 21 Gen 4 can be achieved through simple solutions. Experienced gunsmiths or individuals familiar with firearm maintenance can utilize essential tools to tighten the slide and its corresponding rails.

While the design of the Glock differs from that of 1911, gunsmiths adept at handling various firearm models can quickly resolve the issue.

This quick fix eliminates the rattle and restores confidence in the weapon’s reliability. The primary benefit of addressing the slide rattle is restoring the Glock’s characteristic solid feel during handling and operation.

5. Not Firing Issues:

One of the concerning problems Glock 21 Gen 4 owners may encounter is not firing. This issue can manifest in various ways, including a slide that sticks back after cycling, an unresponsive trigger, or malfunctioning springs.

Despite Glock’s reputation for reliability, even well-built firearms like the Glock 21 Gen 4 may experience hiccups, particularly during the break-in stage.

As a Glock owner, addressing these not-firing issues promptly is essential to ensure the firearm’s optimal performance and safety.


Addressing issues of not firing in Glock 21 Gen 4 pistols requires a systematic approach.

Firstly, it’s crucial to clean and lubricate the firearm regularly. Performing a thorough field strip allows access to critical components for maintenance. During the break-in phase, shooting several hundred rounds to help Glocks, including the Gen 4, loosen up and function more smoothly is recommended.

If the issue persists, consider replacing the factory Gen 4 spring with a lighter aftermarket model. Using a high-quality oil for lubrication can also mitigate potential problems.

Remember, addressing these issues promptly can prevent dire circumstances and ensure your Glock 21 Gen 4 operates reliably.

6. Heavy Trigger Pull Problem:

The Glock 21 Gen 4 is a renowned pistol, but some users encounter a heavy trigger pull issue, affecting their shooting experience. This problem often stems from various components within the firearm.

The trigger mechanism, including the safety trigger, can accumulate debris or experience friction, leading to increased effort required to pull the trigger. Manufacturers design the Glock with safety features like the firing pin and primer to prevent accidental discharges, but excessive friction can hinder smooth operation.

Users may also find that usage over time contributes to a heavier pull, mainly if the firearm is not maintained regularly.

One potential solution involves examining the frame and grip for any misalignment or issues with the pins. Additionally, thorough field stripping allows for a closer inspection of internal components.

Users can also explore aftermarket options to install lighter trigger pull kits, which can alleviate the pain and strain experienced in the hands during shooting sessions.

While some shooters may compare the Gen 4 to its predecessor, the Gen 3, for differences in trigger feel, addressing the heavy pull issue can enhance the overall shooting experience and accuracy.


Solutions for Glock 21 Gen 4 users grappling with a heavy trigger pull vary depending on the severity of the issue.

One approach involves Dremel’s work, where users carefully smooth out the pin area to reduce friction and alleviate the bulge causing the resistance. However, this method requires expertise to avoid damaging the firearm.

Alternatively, exercising caution during field stripping can prevent exacerbating the problem. If the pistol is under warranty, contacting the manufacturer for repairs or a new connector installment may effectively resolve the issue.

Facing a heavy trigger pull can be a source of frustration and pain for shooters, affecting their overall experience. Exploring different choices and seeking professional assistance can lead to a smoother and more satisfying trigger action.

Tested Alternative Guns for Glock 21 Gen 4

1. S&W M&P 45:

The S&W M&P 45 emerges as a formidable contender for Glock 21 Gen 4 enthusiasts seeking versatility and reliability. Boasting a curved trigger and a downward-sloping design, the M&P offers a distinct shooting experience compared to the Glock platform.

Its full-size, double stack 45 magazine capacity ensures ample firepower for various scenarios. However, users may encounter similar issues addressed in Glock 17 problems.

What sets the S&W M&P 45 apart are its ergonomic features tailored for comfort and control. The grip design, meticulously crafted for optimal hand placement, enhances shooting dynamics and reduces fatigue during extended use.

Drawing from personal experience, the S&W M&P 45 impresses with its balanced blend of performance and comfort, making it a worthy consideration for those exploring alternatives to the Glock 21 Gen 4.

2. Springfield XDM 45:

In the realm of alternative firearms to the Glock 21 Gen 4, the Springfield XDM 45 stands out as a compelling option. Despite mixed reviews among firearm enthusiasts, the XDM 45 offers a unique blend of features and performance.

One notable aspect is its trigger pull, which varies in user satisfaction. While some find it to offer precise control, others may perceive it differently based on personal preferences and shooting styles.

Comparing it to the Glock 21 gen 4, the XDM 45 presents a distinct choice for those seeking a long-slide option as a substitute.

3. FNX 45 Tactical:

The FNX 45 Tactical emerges as a formidable contender among alternative firearms for the Glock 21 Gen 4. Renowned for its powerful performance and precise engineering, the FNX 45 Tactical offers shooters a robust platform with enhanced capabilities.

One of its standout features is the large frame, providing a comfortable grip and stable shooting experience.

Unlike some alternatives, the FNX 45 Tactical minimizes issues commonly associated with stock parts, offering reliability and consistency in performance.

Moreover, the FNX 45 Tactical boasts a trigger designed to deliver smooth and responsive firing, contributing to its overall appeal as a reliable alternative to the Glock 21 Gen 4.

My Final Conclusion

Reflecting on the Glock 21 Gen 4 and its inherent problems, it’s essential to consider its role as a home defense weapon. While the G21 offers significant firepower, particularly in its compatibility with +P form 45 ACP ammunition, it’s not without its drawbacks.

One notable issue is its compatibility with low-pressure and subsonic 230-grain ammo.

Despite its versatility, the Glock 21 Gen 4 may only sometimes handle these variations with optimal lethality, particularly in comparison to other cartridges like the 38 special.

Moreover, when considering its potential for suppressed use, the G21’s performance may vary.

While it maintains its size advantage over alternatives like the G19 and G23, its effectiveness, when suppressed, is a point of contention among weapons enthusiasts.

In my experience, while the Glock 21 Gen 4 is a reliable firearm in many respects, its performance nuances must be understood within the context of its intended use and the specific cartridge it fires.

My Friends Feedback

In discussing the Glock 21 Gen 4 and its problems, I’ve gathered insights from various users in my circle. Their experiences span a range of perspectives, highlighting both the good and bad aspects of this firearm.

Some users have noted the need to change the stock sights for better accuracy, particularly during the 2005-06 period when Glock models underwent significant changes. However, many acknowledge its durability and reliable performance as a service-grade pistol despite this.

Renowned firearms expert DocGKR has also approved the Glock 21 Gen 4, primarily when chambered in 10mm.

They report that it shoots smoothly and efficiently, although some have experienced dependability issues during the initial years, mainly due to a flawed magazine design. If you’re experiencing similar challenges, consider solutions for Glock 48 problems.

However, Glock has been responsive to feedback, with some users noting improvements after six months of the original design. Introducing new magazines addressed lethality and size, which some found to be too big for comfortable carrying, preferring models like the G19 and G23 for everyday weapons.

Despite its tremendous aesthetic appeal, a few have found the Gen4 iteration disappointing initially. However, its performance has been redeemed for others, making it their absolute favorite among the masses of available firearms.

Furthermore, when discussing the Glock 21 Gen 4 and its problems, it’s crucial to consider the experiences of owners who have handled millions of firearms.

While statistics can be informative, they’re not the whole picture. Owning a Glock is not like winning the Powerball; it’s not about profit but rather understanding the numerator and denominator in the equation of firearm value.

For many, the likelihood of encountering issues with their pistols is just noise amidst their overall satisfaction. These are trusted weapons enjoyed for YEARS, not simply garbage to be discarded at the first sign of an Internet complaint.

The reduction in performance with Wolf aftermarket barrels or certain reloads with lead bullets is not a blanket condemnation of the Glock’s reliability. Even with malfunctions, the Glock 21 Gen 4 remains a stalwart handgun in the eyes of many owners.

Ultimately, the slingshot maneuver and some play may be the only problems worth noting amidst the Glock 21 Gen 4’s arsenal of capabilities.

Common Questions Asked About Glock 21 Gen 4

Is Glock 21 Gen 4 reliable?

G21 gen 4 have all been 100% reliable over combined ~5k rounds. zero stoppages.

Why don’t people like Gen 4 Glocks?

Three of the most common problems being directly related to the change in frame and grip dimensions.

Is A Glock 21 a good gun?

It has proven itself to be a reliable, accurate, and durable weapon.

What is the Glock 21 known for?

Remarkable for its accuracy and light recoil

Can you pocket carry Glock 21 Gen 4?


Does Glock 21 carry a threaded barrel?


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