15 Common Umarex MP40 Problems (With Fixes)

Hi dear visitor welcome to our blog. 

Umarex MP40 is one of the best brands in the world of guns. 

But some people face problems with this model. 

In this guide, we explain 15 common Problems of this model with unique solutions. So let’s start now.

Umarex MP40 Problems

Umarex MP40 Problems

The Umarex MP40, while an excellent airgun, is not without its issues. One of the most common problems users encounter is jamming, often caused by the misalignment of BBs.

This can be mitigated by ensuring proper loading of the magazine. Additionally, some users have reported occasional gas leakage, which may require professional repair or replacement of parts.

1. Failure to Feed


The “Failure to Feed” issue often arises due to improper loading of the magazine or the use of low-quality ammo. 

Incorrect feeding of BBs into the magazine or damage to the magazine spring can lead to this issue. 

Besides, the use of BBs that are not well-rounded or contain defects can cause them to jam, leading to a feed failure.


The solution to this problem primarily involves checking and correcting the magazine loading process. 

Make sure that the BBs are loaded correctly into the magazine, ensuring they form an uninterrupted line. If damage to the magazine spring is the issue, consider replacing the magazine

Lastly, always opt for high-quality, well-rounded BBs to minimize the chance of jamming and subsequent feeding failures.

2. Misfire Issues


Misfire issues with the Umarex MP40 are typically a result of improper maintenance of the firearm, leading to an accumulation of fouling in the barrel, or the use of substandard BBs

This can interfere with the gun’s mechanism, causing it to fire inaccurately or not at all. 

Also, weak or damaged springs in the firing mechanism can also lead to misfires.


To rectify misfire issues, ensure that your Umarex MP40 is cleaned and oiled regularly to prevent the build-up of fouling. High-quality BBs should be used to ensure smooth operation. 

If the issue persists, it may be necessary to inspect and replace any weak or damaged springs in the firing mechanism. 

Regular checks and maintenance of the firearm are essential for preventing misfire issues and ensuring optimal performance.

3. Jamming Problems


Jamming problems with the Umarex MP40 can often be traced back to poor ammunition selection or a dirty firearm

Using low-quality BBs can cause the gun to jam, as can a build-up of dirt or fouling within the barrel or firing chamber. 

Improper loading of the BBs into the magazine can also lead to jamming problems, as it may disrupt the feed mechanism.


Preventing and solving jamming issues involves a commitment to regular maintenance and cleaning of your Umarex MP40

It’s vital to remove any built-up dirt or fouling from the barrel and firing chamber. The use of high-quality BBs is paramount to ensure smooth function. 

Furthermore, make sure to load the BBs correctly into the magazine to prevent disruption of the feed mechanism. 

Regular care and proper handling of the firearm will significantly reduce the likelihood of jamming problems.

4. Inconsistent Velocity


Inconsistent velocity in the Umarex MP40 can be attributed to a number of factors, most commonly to irregular air pressure or the use of various BB weights

Fluctuating air pressure in the gun could lead to inconsistent shooting speeds. 

Similarly, using BBs of different weights can cause varying degrees of velocity, as lighter BBs tend to move faster than their heavier counterparts.


To tackle the issue of inconsistent velocity, ensure a stable air pressure in your firearm. 

Regular checks and maintenance of the air pressure mechanism can go a long way in maintaining consistent velocity. 

Furthermore, it is recommended to stick to BBs of a uniform weight to ensure an even shooting speed. 

Consistency in ammunition weight and stable air pressure are essential for maintaining velocity consistency in the Umarex MP40.

5. Poor Accuracy


Poor accuracy when firing the Umarex MP40 can often be attributed to improper alignment of sights, imperfect gun handling, or the use of low-quality BBs

A misaligned sight can skew the trajectory of the BB, leading to inaccurate shots. Similarly, improper handling of the firearm can cause the barrel to move off target during firing. 

Further, substandard BBs can have irregular shapes or uneven weight distribution that affects their flight path.


To improve accuracy, first ensure that your sights are correctly aligned. This can be achieved by referring to the user manual or seeking professional help. 

Secondly, practice steady gun handling to keep the firearm stable when firing. This can involve using both hands, bracing against a solid surface, or using a firearm support. 

Lastly, always opt for high-quality BBs that are consistent in shape and weight, thereby ensuring a predictable trajectory. 

Regular practice and adherence to these guidelines can significantly enhance your shooting accuracy with the Umarex MP40.

6. Trigger Malfunction


Trigger malfunction in the Umarex MP40 typically arises due to a lack of proper maintenance or the presence of debris within the trigger mechanism

Over time, grime and fouling can accumulate within the trigger assembly, leading to stiffness or failure to actuate. 

Furthermore, wear and tear or damage to the trigger components can also result in malfunction.


Addressing trigger malfunction involves regular cleaning and inspection of the trigger assembly

Make sure to meticulously clean the trigger mechanism, removing any dirt or fouling that might obstruct movement. 

If cleaning does not resolve the issue, inspect the trigger components for any signs of damage. In case of wear or damage, replacement of the faulty part(s) is recommended. 

Always remember, a well-maintained firearm is key to preventing trigger malfunction.

7. Difficulty in Loading BBs


Difficulty in loading BBs into the Umarex MP40 can often be due to improper handling, misaligned magazines, or faulty BBs

Improper handling during the loading process can cause BBs to jam or not sit correctly within the magazine. 

Misaligned magazines may not accept BBs smoothly, causing difficulty during loading. 

Furthermore, BBs with irregular shapes or sizes caused by manufacturing defects may not fit well into the magazine, leading to loading issues.


To overcome this issue, it is crucial to handle the firearm and BBs correctly during the loading process

Ensure the magazine is aligned properly before loading and load BBs gently to prevent jamming. 

Always use high-quality BBs that are consistent in shape and size. If the issue persists, inspect the magazine and the BBs for any signs of damage or defects. 

Regular inspection and careful handling are key to preventing loading difficulties with your Umarex MP40.

8. CO2 Leakage


CO2 leakage in the Umarex MP40 is generally the result of improper cartridge installation, worn-out seals, or faulty CO2 cartridges

Incorrect installation of the CO2 cartridge can lead to improper sealing and cause leakage.

 Similarly, over time, the seals in the CO2 chamber can wear out and fail to hold the gas securely. Lastly, a faulty or damaged CO2 cartridge can also be a source of leakage.


To prevent and fix CO2 leakage, first, ensure the correct and careful installation of the CO2 cartridge. Always follow the instructions provided in the user manual. 

Secondly, regular inspection and replacement of the seals in the CO2 chamber is crucial to prevent leakage. 

Consider consulting a professional if you are unsure about the condition of the seals. Lastly, always use high-quality CO2 cartridges and inspect them for any signs of damage before use. 

Maintaining your firearm’s CO2 system is essential to prevent leakage and ensure smooth operation.

9. Defective Safety Mechanism


The safety mechanism in the Umarex MP40 can become defective due to improper usage, lax maintenance, or internal wear and tear

Inappropriate handling of the firearm can lead to undue strain on the safety mechanism, causing it to malfunction. 

Neglecting regular maintenance can result in dust, grime, or rust compromising the working of the safety features. 

Further, natural wear over time can degrade the internal components, leading to a faulty safety mechanism.


To rectify a defective safety mechanism, it is imperative to handle your firearm with care, adhere to a routine maintenance schedule, and regularly assess for internal wear and tear

Ensure you are using your firearm as instructed by the manufacturer to avoid placing unnecessary strain on the safety mechanism. 

Regular cleaning and lubrication can prevent the accumulation of dust and rust that may cause malfunction. 

Lastly, have your firearm inspected periodically by a professional to address any internal wear before it becomes a significant issue. 

Proper usage, maintenance, and inspection are the cornerstones of a reliable safety mechanism.

10. Loose Magazine Release


A loose magazine release in the Umarex MP40 often results due to frequent heavy use, inadequate maintenance, or internal component wear

Frequent and heavy use of the magazine release can lead to it loosening over time. 

Inadequate maintenance can result in the accumulation of grime and rust, causing the release mechanism to malfunction. 

Also, the internal components responsible for the secure fit of the release may wear down with time, leading to a loose magazine release.


To rectify a loose magazine release, regular maintenance, cautious handling, and periodic inspection of components are essential. 

Ensure you clean and lubricate the magazine release thoroughly during routine firearm maintenance. 

Handle the magazine release carefully during use to prevent undue wear and tear. 

Finally, have a professional inspect the internal components of the release mechanism periodically to ensure their integrity and replace them if necessary. 

These measures can help maintain a firm and responsive magazine release.

11. Damaged Front Sight


A damaged front sight on the Umarex MP40 can be a consequence of rough handling, inadequate care, or normal wear and tear

Frequently exposing the firearm to rough conditions can lead to scratches or breaks on the front sight. 

Failing to provide adequate care and maintenance may result in rust or corrosion damaging the sight. 

More, over time and use, the front sight may naturally degrade, leading to visual imperfections or functional failure.


Counteracting a damaged front sight involves gentle handling, rigorous maintenance, and regular checks for wear and tear

Always handle your firearm with utmost care and respect to prevent unnecessary damage. Regular cleaning and maintenance can help ward off rust and corrosion that could impair sight. 

Also, periodically check the front sight for signs of wear and degradation, and have it replaced by a professional if necessary. 

Remember, preserving the condition of the front sight is integral to accurate shooting.

12. Stock Adjustment Problems


Stock adjustment issues with the Umarex MP40 typically arise due to improper handling, lack of maintenance, or general wear and tear

Rough or careless handling can disrupt the adjustability of the stock, making it hard to modify as needed. 

A lack of regular cleaning and maintenance can allow dust, grime, or rust to interfere with the adjustment mechanism. 

Over time, the natural wear and tear can wear down the components involved in stock adjustment, leading to malfunctions.


Addressing stock adjustment issues involves proper handling, consistent maintenance, and routine inspections for damage or wear

Always handle the firearm with care, particularly when adjusting the stock, to prevent undue strain on the mechanism. 

Regular cleaning and lubrication help keep the adjustment mechanism functioning smoothly, and free from dust, grime, or rust. 

Furthermore, engage a professional to periodically inspect the firearm, assessing the mechanism for any signs of wear or damage that could impede stock adjustment. 

Indeed, safeguarding the adjustability of the stock is paramount to a comfortable and customized shooting experience.

13. Rough Bolt Action


A rough bolt action in the Umarex MP40 can emerge as a result of improper firearm handling, inconsistent maintenance, or natural degradation

Careless or rough handling can damage the bolt, hindering its smooth movement. 

Inconsistent maintenance can lead to the accumulation of dust or rust, causing friction that makes the bolt action rough. 

Further, regular use can naturally wear down the bolt over time, impeding its fluid movement.


To remedy a rough bolt action, you should follow a consistent practice of careful handling, regular maintenance, and periodic professional inspections

Always handle your firearm gently to prevent any damage to the bolt. Regular cleaning will prevent dust and rust that can impede smooth bolt action. 

Finally, have a professional assess the bolt for wear and tear, and replace it if necessary. 

Proper handling, routine maintenance, and ongoing inspections will ensure a smooth and efficient bolt action in your firearm.

14. Frequent Gas Exhaustion


Frequent gas exhaustion in the Umarex MP40 could be due to improper handling, inconsistent maintenance, or inherent design inefficiencies

If handled improperly, the gas canister could be inadvertently released, causing rapid gas exhaustion. 

Inconsistent maintenance could lead to issues with the gas system, such as leaks or malfunctions, resulting in gas exhaustion. 

Furthermore, the firearm could have design inefficiencies which lead to excessive gas usage, causing it to run out frequently.


To mitigate frequent gas exhaustion, practice proper handling, and consistent maintenance, and consider aftermarket upgrades, if necessary. 

Handle your firearm carefully to ensure the gas canister is secure and not accidentally released. 

Incorporate regular maintenance and checks for gas system issues into your firearm care routine to prevent leaks or malfunctions. 

If the gas exhaustion persists, consider researching and investing in aftermarket upgrades to enhance gas efficiency

Remember, preventing frequent gas exhaustion not only prolongs firing sessions but also reduces the long-term maintenance cost.

15. Improper Blowback Function


The improper blowback function in the Umarex MP40 typically results from inadequate maintenance, poor handling, or inherent mechanical issues

Inadequate or irregular maintenance could lead to a build-up of dust and debris in the blowback mechanism, hindering its operation. 

Poor handling can result in unnecessary wear and damage, affecting the blowback function. Furthermore, inherent mechanical issues could cause persistent problems with the blowback.


To address an improper blowback function, adhere to a regimen of meticulous maintenance, respectful handling, and periodic expert assessments

Regular cleaning and maintenance are key to preventing build-up that can disrupt the blowback function. 

Handle your firearm with care and respect to avoid unnecessary damage. If problems persist, engage a firearms expert to inspect and rectify any potential mechanical issues

Remember, a correctly functioning blowback is crucial to the overall performance and reliability of your firearm.


It becomes increasingly clear that the considerations we’ve discussed are of integral importance. 

The various elements intertwined in our discussion not only shed light on multiple perspectives but also emphasize the need for a comprehensive approach. 

Through a balanced and thoughtful analysis, we should be able to navigate the complexities of this subject matter. 

More research is needed in some areas to fully grasp the depth and breadth of the issues at hand. 

Nevertheless, the discourse has laid a solid foundation for further exploration and understanding.


Q1: Is the Umarex MP40 good?

Yes, the Umarex MP40 is known for its authentic design and robust construction which makes it a popular choice among enthusiasts.

Q2: What is the fire rate of the Umarex MP40?

The fire rate of the Umarex MP40 is approximately 450-550 rounds per minute.

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