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Common Reasons AR-15 Bolt Won’t Lock Back and How to Fix

The bolt not locking back on your AR-15 is a common problem most shooters encounter. It comes down to a few different component problems, and if you are meticulous about maintenance, you can keep the rifle in good working order for years. So why won’t your AR-15 bolt lock back into place, and how can you fix it?

The most common reasons a bolt won’t lock back on an AR style rifle is because the weapon is dirty, the bolt lock/release is faulty, the weapon is under-gassed, or the magazine is preventing proper function.

The moving parts in a rifle are critical to its proper function. Unfortunately, when these parts become dirty or worn, the gun can exhibit problems, like the bolt not locking back. So read on and learn everything you need to know about why your bolt won’t lock back and how to fix it.

Reasons an AR-15 Bolt Won’t Lock Back

When dealing with sporting rifles, you can first expect a bit of a learning curve. Different setups and ammo combinations make the rifles have different capabilities. These setups can often make your rifle act in ways you haven’t seen before and unveil problems you never knew existed.

The main reasons that an AR-15 bolt isn’t locking back are:

  • Cleanliness – If your rifle isn’t clean, it will cause the bolt to jam forward. You might think it would jam backward, but built-up carbon scoring on the bolt often causes it to remain in place after connecting with the round. Use rags, oil, and a cleaning kit to delve into the nooks and crannies to allow the bolt to move freely.
  • Faulty Lock – Depending on what company makes your rifle, the locking mechanism could be different than the standard AR. For example, the Colt model has a locking mechanism trigger that allows you to slide it back, and the bolt remains in place. If your trigger isn’t working, you should do some inspection and replace it if necessary.
  • Gas Issues – The AR-15 is a gas-powered rifle. When the mechanisms don’t work as they should, there’s a high probability that the gas that powers their function was diverted or didn’t reach the area intended.
  • Magazines – Another culprit of bolts not locking back is magazines. They can be made from different materials and in various sizes, giving your rifle fits. Find mags that don’t allow the bolt to close after the last round is fired.

When the bolt doesn’t lock back, it is much harder to see what is going on in the chamber and magazine well. Often when there are ejection or misfire issues, by looking in these two places, you can find the problem and begin to devise a way to fix it. Always be careful when dealing with chambered rounds, as they could go off and hurt someone.

Can you Lock the Bolt Back on an AR-15?

You can easily lock the bolt back on your rifle by triggering the bolt catch when the charging handle is pulled back. You must ensure that the charging handle is pulled back, and you will know when it gets there by the satisfying click it makes. Once you hear the click, you can thumb the bolt catch switch.

How Does an AR-15 Bolt Lock?

Locking the bolt back on your AR-15 gives you access to the inner workings of the rifle without stripping it down. This allows quick inspections and safety checks to see if anything critical has occurred in the gun. Critical malfunctions can be dangerous. Always practice muzzle awareness and never point a gun at anything you don’t want to kill.

The steps to lock back the bolt on your AR-15 are:

  • Drop the Magazine – The first thing to do is ensure no rounds in the magazine or the chamber. Drop your mag and check the openings to ensure that there’s nothing in there. Once you have done a visual check, stick your fingers in and see if you feel anything. Be sure there’s nothing in the magazine well or protruding from the chamber.
  • Pull the Charging Handle – Once the mag is dropped, you can grip the charging handle and pull it all the way back. If you are working with a built rifle, ensure the charging handle is appropriate, as one that doesn’t fit won’t allow the bolt to be pulled back far enough to catch it.
  • Hear the Click – Once the handle is pulled back far enough, there will be a slight click. This click lets you know that the handle has moved the bolt back as far as possible. Remember that if you are using a built rifle, it must have the correct charging handle, or the weapon will not lock back.
  • Thumb the Catch – There’s a tiny nodule on the rifle near the back. This is the location of the bolt catch. The bolt catch will move inward when toggled, and the weight from the bolt will hold it in place.

Locking back the bolt is a simple procedure that creates a safe environment for you. If the bolt triggers and there’s a live round in the chamber, it will go off. Make sure that no matter what is going on with the bolt, you point the rifle in a safe direction.

Why is my Bolt not Closing All the Way?

Usually, when the bolt doesn’t close, it is either an ammo or spring issue. An overloaded magazine will keep the rounds from seating perfectly, and the rifle will not go back into battery. Bad springs mean there isn’t enough force to close the bolt, and there will be a bit of space between it and the chamber.


It can be frustrating when your bolt won’t lock back on your AR-15. The main culprits are cleanliness and faulty mechanics. Keeping the rifle clean, you protect against wear, and regular inspections mean you catch things before the gunsmith has to step in.

Repairing the rifle is always an easy fix. So easy that most people who have tools around the garage can repair bad springs and replace charging handles that aren’t correct.

Rifles are technical; if you are a novice gunsmith watching videos on YouTube could be the way to go. I would start with the Neckbone Armory YouTube Channel found here.