Mossberg 100 ATR Problems And Their Solutions

The Mossberg 100 ATR is a popular rifle that has been around for decades, providing gun enthusiasts with unparalleled accuracy and reliability. However, like any other firearm, it can experience some problems that can cause headaches for its users.

In this guide, we will discuss some of the most common problems that you may encounter with your Mossberg 100 ATR and provide practical solutions to help you overcome these issues. It is essential to have a good understanding of your rifle, so let’s dive in.

Some of the most common problems with Mossberg 100 ATR include Misfires, Firing Pin Light Strike, Trigger Slack, Magazine Problems, Bolt problems, Jamming Problem and Accuracy Issue.

Common Mossberg 100 ATR Problems And Their Solutions

1. Misfires

Misfire is one of the most common problems that shooters encounter when using Mossberg 100 ATR rifles. It happens when the gun fails to fire a round even after pulling the trigger. If you experience this issue, don’t worry, as there are various solutions that can help you solve it.

First and foremost, check your ammunition and make sure it is not old or damaged. Sometimes, old shells can cause misfires due to deterioration of the primer or powder inside. If that’s not the case, try using a different type of ammunition as some rifles tend to be picky with certain brands.

If your ammunition is fine and you still experience misfires, it could be an issue with your firing pin. Check if there is any debris or residue built up around the pin, as this can cause it to malfunction. You can clean it with a soft cloth or brush and some gun cleaning solution.

Another possible cause of misfires is an aftermarket modification that may have been done to your rifle. If you have altered any parts of your Mossberg 100 ATR, such as the trigger assembly or bolt, it could be the reason for misfires. In this case, you should consult a gunsmith to properly adjust or remove the aftermarket parts.

2. Firing Pin Light Strike

One of the most common problems faced by Mossberg 100 ATR owners is a failure to fire, known as a light strike. This occurs when the firing pin does not hit the primer forcefully enough to ignite the cartridge.

Possible Causes:

  • The firing pin may be dirty or covered in oil.
  • The bolt assembly may be loose or not properly seated.
  • The firing pin spring may be worn or damaged.


  1. Begin by cleaning the firing pin with a cloth and some gun cleaner. This should remove any dirt, debris, or excess oil that may be preventing it from striking forcefully.
  2. Check the bolt assembly and make sure it is properly tightened and seated in place. If not, tighten any loose screws or reseat the bolt assembly.
  3. If cleaning and tightening do not solve the issue, it is possible that the firing pin spring may be worn or damaged. In this case, it will need to be replaced by a professional gunsmith.

3. Trigger Slack

One of the most common issues faced by Mossberg 100 ATR owners is trigger slack. Trigger slack refers to the amount of movement or play in the trigger before it breaks and releases the firing pin. This can be an annoying problem for shooters, as it can affect accuracy and consistency in shooting.

What causes trigger slack?

Trigger slack can be caused by a variety of factors, including worn or damaged trigger components, improper installation of the trigger assembly, or simply poor manufacturing.

Solutions for fixing trigger slack

  1. Inspect and clean the trigger components: The first step in addressing trigger slack is to inspect and clean all the components of your Mossberg ATR’s trigger system. This includes the sear, hammer, and trigger itself. Any buildup of dirt, debris, or rust can cause the trigger to have more play than necessary. Use a gun cleaning kit to thoroughly clean all the components and ensure they move smoothly.
  2. Check for wear and tear: If your Mossberg 100 is an older model or has been heavily used, it’s possible that certain trigger components have worn down over time. In this case, it may be necessary to replace these components with new ones.
  3. Adjust trigger pull weight: Some shooters prefer a lighter or heavier trigger pull, but adjusting the trigger pull weight can also help reduce trigger slack. Consult your 100 ATR manual for instructions on how to adjust the trigger pull weight.
  4. Consider aftermarket trigger parts: If you are still experiencing trigger slack after trying the above solutions, you may want to consider investing in aftermarket trigger components. Many companies offer replacement triggers that are designed to improve the overall performance of your 100 ATR.

4. Magazine Problems

Magazines are an essential part of any firearm, as they hold the ammunition and keep your gun functioning. However, sometimes they can cause problems that hinder your shooting experience.

Problem #1: Magazine Not Feeding Properly

One of the most significant issues with magazines is when they fail to feed rounds into the chamber smoothly. This problem can cause interruptions and affect your shooting accuracy.

Solution: The first thing you should do is check if your gun is clean and properly lubricated. If the issue persists, try using a different type or brand of ammunition as some may not work well with your rifle. Another option is to adjust the feed lips of your magazine. You can do this by carefully bending them inwards or outwards with pliers.

Problem #2: Magazine Falls Out

Another common problem with magazines is when they fall out of the gun during shooting. This issue can be dangerous as it may cause accidental discharge and harm you or others around you.

Solution: Make sure that your magazine is properly inserted and locked into place before shooting. If the problem persists, you can try tightening the magazine catch using a screwdriver or replacing it if necessary.

Problem #3: Round Jams in Magazine

Sometimes, a round may get stuck in the magazine, making it difficult to load or unload ammunition properly.

Solution: Check if there are any obstructions or debris inside the magazine that may be causing the jam. If it’s clear, try cleaning and lubricating your magazine. If the problem continues, you may need to replace the spring or follower in your magazine.

Problem #4: Magazine Capacity

As an ATR owner, you may have noticed that your rifle’s magazine capacity can seem a bit limited. This issue can be frustrating, especially when shooting competitions or hunting trips.

Solution: While it’s not recommended to alter the capacity of your magazine, you can purchase extended magazines from reputable brands that are compatible with your rifle. Make sure to check local laws and regulations before doing so.

5. Bolt Problems

The bolt can sometimes get sticky, especially after long periods of not cleaning the rifle. You’ll want to regularly disassemble the bolt and clean out any built-up grime or residue that could be slowing it down. Using a quality gun solvent and brush to scrub the bolt parts clean should have it smooth as new in no time.

Another thing to check is that the firing pin is moving freely. Remove the bolt and try pushing the firing pin in and out with your finger. It should slide smoothly. If not, a little cleaning and lubrication should loosen it up. Don’t force the firing pin though, as it could break.

Issues feeding or ejecting rounds are also common with semi-auto rifles like the Mossberg 100 ATR. Be sure to clean the chamber and barrel regularly to prevent buildup that could impede the rounds. Also inspect the extractor claw for any damage or worn springs that could cause it to slip on the casings.

6. Jamming Problem

Dealing with a jam can be frustrating, but don’t worry – it’s usually an easy fix with the Mossberg 100 ATR. Here are some tips if you experience jamming:

  • First, make sure you are using high-quality ammunition that is appropriate for the caliber of your rifle. Poor ammo quality can cause feed and extraction issues. Stick to major brands to avoid this.
  • Check that your magazine is cleaned, lubricated, and inserted properly. A dirty or faulty magazine is one of the most common causes of jams. Take it out and wipe it down thoroughly.
  • The chamber and action may be dirty or gummed up, preventing smooth cycling. You’ll want to clean these areas well including the bolt face and ejection port.
  • Inspect the extractor and ejector parts of the bolt. Built up grit or a weakened spring can impede their ability to smoothly remove spent casings. A little cleaning and lubrication can get these moving freely again.
  • If issues persist, a gunsmith can polish and tune the chamber and feed ramps which may have burrs or roughness causing hang-ups’.

7. Accuracy Issue

Another most  common causes of poor accuracy are a dirty bore, poor scope mounting, and poor ammunition quality. Here’s what I recommend trying:

Clean the bore thoroughly – Use a good copper solvent and bore brush to scrub out any built-up copper fouling or carbon in the rifling. This can really affect accuracy if left dirty.

Check scope mounting – Make sure your scope rings are tight and the proper height. Any wiggle or misalignment here will throw off your shots. You may need high scope rings for the 100 ATR.

Use quality ammo – Stay away from cheap bulk ammo for hunting and make sure to match your ammo to the rifle’s twist rate. Try a few different loads to see what shoots best.

If those don’t fix your accuracy problems, it could be a bedding or crown issue. You may want to have a gunsmith look at bedding the action or recrewing the muzzle if the crown got damaged.

Frequently Asked Questions(FAQs)

How can I address misaligned sights on my Mossberg 100 ATR?

To address misaligned sights, it’s important to ensure that the sights are properly aligned and adjusted according to the manufacturer’s specifications.

Is the Mossberg 100 ATR a reliable rifle for hunting and range shooting?

The Mossberg 100 ATR is generally considered reliable for hunting and range shooting, especially when properly maintained and adjusted for specific shooting conditions.

What routine maintenance should I perform on my Mossberg 100 ATR?

Routine maintenance for the Mossberg 100 ATR should include regular cleaning of the barrel, inspection of moving parts, and ensuring proper lubrication for smooth operation.

How should I align the sights on my Mossberg 100 ATR for consistent accuracy?

Aligning the sights on the Mossberg 100 ATR should be done specifically according to the manufacturer’s guidelines to achieve consistent accuracy and reliable performance.

Can I depend on the Mossberg 100 ATR for consistent performance in multiple shooting scenarios?

A: When properly maintained and managed, the Mossberg 100 ATR can deliver consistent performance in multiple shooting scenarios, provided the rifle is set up and adjusted for each specific scenario.


So, there you have it! You now know all about the Mossberg 100 ATR and the common problems that can occur with this rifle. But don’t be discouraged – every rifle has its issues, and most of these problems can easily be solved with a little bit of knowledge and some simple fixes.

Remember to always thoroughly clean your rifle after each use, and keep an eye out for any signs of wear or damage. Regular maintenance and inspections can help prevent most of these problems from occurring in the first place.

If you do encounter any issues with your Mossberg 100 ATR, don’t panic. Refer back to this guide and try out the solutions we’ve provided. And if all else fails, don’t hesitate to take it to a professional gunsmith for further assistance.

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