How to Remove the Outer Barrel on an Airsoft M4 Rifle?

Airsoft guns are replica firearms used for sport, recreation, and training. The M4 rifle is one of the most popular airsoft guns on the market. Like real steel firearms, airsoft M4s have multiple components that occasionally require disassembly for maintenance and repairs. One such component is the outer barrel. Removing the outer barrel on an airsoft M4 gives access to the inner barrel and hop-up unit for cleaning and upgrades. It can seem daunting if you’ve never done it before, but the process is quite straightforward.

In this step-by-step guide, I’ll walk you through the complete process of removing the outer barrel on an airsoft M4, using common tools. We’ll also discuss reasons why you may need to remove the outer barrel, what to watch out for, and reassembly tips. Let’s get started!

When Do You Need to Remove the Outer Barrel?

Here are some of the main reasons why removing the outer barrel on your airsoft M4 may be necessary:

  • To access the inner barrel and hop-up unit for cleaning and maintenance
  • To upgrade the inner barrel and/or hop-up unit
  • To repair a damaged outer barrel
  • To swap out handguards or free float rail systems
  • For advanced users, to install aftermarket gas blowback kits

It’s generally good practice to remove and clean the inner barrel and hop-up unit periodically to keep your airsoft M4 shooting straight and accurate. Upgrading these components can also boost range and accuracy.

Safety First!

Before disassembling any airsoft gun, make sure to:

  • Put on ANSI Z87.1 eye protection
  • Remove the magazine
  • Ensure the chamber and barrel are completely clear of any BBs
  • Verify the gun is on “safe”

This eliminates the very small risk of an accidental discharge while working on the gun.

What You’ll Need?

To remove and later reinstall the outer barrel on your airsoft M4 rifle, you’ll need the following tools:

  • A 1.5mm hex key
  • A punch or thin screwdriver
  • Standard cross-head screwdriver
  • Optional: a vise to securely hold the upper receiver

Now let’s go step-by-step through the process.

Step 1 – Separate the Upper and Lower Receivers

Start by separating the two main components of the M4 – the upper receiver and the lower receiver.

On most M4 airsoft guns, there is a large pin towards the back of the gun that joins the two receivers together.

Use a 1/8” punch and a small hammer to tap out this pivot pin. It may be quite tight, so placing the gun in a vise can help.

Once the pivot pin is out, the upper and lower receivers will separate. Set the lower receiver aside for now so we can focus on the upper receiver and outer barrel.

Step 2 – Remove the Handguard

The handguard (or foregrip) attaches to a delta ring at the front of the upper receiver. We need to detach the handguard to reveal the outer barrel underneath.

Start by unscrewing the small screw underneath the triangular end cap at the rear of the handguard. This screw clamps the handguard in position.

Slide the delta ring back towards the upper receiver. You will then be able to slide the handguard forward off of the delta ring mounting points.

Set the handguard aside and we’ll reinstall it later.

Step 3 – Detach the Outer Barrel

With the handguard removed, you’ll see the full outer barrel exposed.

Locate the barrel nut which joins the barrel to the upper receiver. It’s a large nut with notches located just forward of the receiver itself.

Insert a punch into one of the notches to prevent the nut from spinning. Then, use a screwdriver to turn the nut counterclockwise.

You may need to hold the punch firmly as the nut can be very tight. Keep turning the nut until it is completely detached.

Grip the front of the outer barrel and slide it forward out of the upper receiver. You may need to twist it gently from side to side if sticky.

Step 4 – Inspect and Clean the Barrel Components

With the outer barrel fully removed, you now have access to all the inner components at the front of the airsoft gun.

Use a suitable cleaning rod and cloth to wipe out the interior of the outer barrel. Check for any debris, damage, or unusual wear.

The inner barrel and hop-up unit can also be accessed and cleaned once the outer barrel is off. Refer to your M4 model’s instruction manual for precise details on disassembling the hop-up unit.

Step 5 – Reinstall the Outer Barrel

Reinstallation of the outer barrel simply reverses the removal process:

  • Insert the rear end of the barrel back into the upper receiver. Align the barrel nut threads.
  • Hand thread the barrel nut clockwise until tight. Finish tightening with a screwdriver if necessary.
  • Slide the handguard back over the delta ring alignment tabs.
  • Insert the rear handguard retention screw and tighten it back down.
  • Rejoin upper and lower receivers with pivot pins. Ensure the gun functions safely.

Tips for Outer Barrel Maintenance

Here are some additional tips regarding maintaining and upgrading your airsoft M4 rifle’s outer barrel:

  • When removing or installing the barrel nut, be very careful not to lose the small steel or nylon alignment tab that fits inside the nut. This prevents over-tightening.
  • Periodically check that the outer barrel is aligned straight with the upper receiver and inner barrel. If knocks or damage have caused it to become misaligned, accuracy will suffer.
  • For best accuracy, a quality precision inner barrel with good crowning is recommended. Popular upgrades are Prometheus or PDI stainless steel barrels.
  • Always use plastic-safe cleaner and avoid solvents on outer barrels with an anodized finish. Solvents can damage the surface.
  • When free-floating the barrel, ensure no contact with the handguard which can affect vibration and recoil.
  • There are many custom M4 outer barrel options on the market when building a custom airsoft gun. Barrels now come pre-threaded for flash hiders, in multiple lengths, cuts, and finishes.

Troubleshooting Common Airsoft M4 Issues

If you’re having issues with your airsoft M4 like reduced power, poor accuracy, or excessive recoil, examining and possibly replacing the outer barrel can help identify and resolve problems:

Reduced Power: A damaged or misaligned inner barrel or improperly seated hop-up bucking can cause compression issues that reduce power. Inspect these components closely once the outer barrel is removed.

Poor Accuracy: Bad crowning, small dents, and debris in the inner barrel can degrade BB consistency. A bent or damaged outer barrel itself can also throw shots off target.

Excessive Recoil: If your M4 slams back into your shoulder harder than it seems like it should, the cause may be an aftermarket metal outer barrel adding excessive mass weight up front. Revert to a standard lightweight polymer barrel.


Removing the outer barrel on an airsoft M4 rifle allows access to key components that have a major impact on performance. With a few simple tools and proper procedures, the job can be performed quickly and safely.

Periodically removing and cleaning the barrel assembly keeps the gun shooting straight and hitting targets. It also allows complex upgrades like precision inner barrels and hop-ups to be installed.

Hopefully, this guide gave you the step-by-step process and tips needed to comfortably maintain your airsoft rifle outer barrel yourself. Accurately shooting tiny plastic BBs hundreds of feet requires tight tolerances, so taking the time to periodically clean and inspect will keep your gun always performing at its best!

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