Relevant Kit Revisions

The advice in this article is relevant to all DGA M249 kits that are 5th generation or older.

Symptoms

After installing the barrel group into the gun, including using the barrel latch, the barrel group falls out of the gun after firing or when pointed down.

Causes

The primary cause for this particular problem is neglecting the DGA engine barrel locking system in favour of the original donor system.

On the original, unmodified AEG, the barrel retention latch grabs and retains the entire barrel group on the gun. Users who install the barrel assembly assuming the original latch will hold the barrel in place are mistaken.

On DGA M249 builds, the barrel latch does come into play, and does provide some amount of positive retention. On a DGA M249 build, one set screw holds the barrel group locked to the engine and the body. If this set screw is not installed, or not tightened, then the original latch by itself cannot hold the barrel group in place and allows it to slide out of the receiver.

This issue can often be encountered if you have recently adjusted your hop up and have forgotten to reinstall the set screw, or if you removed the set screw during assembly and didn't reinstall it.

Solutions

You can solve this issue by installing and/or tightening the barrel group retention set screw. If your screw is missing, or keeps backing out, replace it with a longer one such as an M4x4 or M4x6.

You will need:

• 2mm hex driver
• Blue thread lock, such as Loctite 243 or 244
• Original M4 set screw, or replacement M4x4 or M4x6 set screw

Please follow these steps to install the set screw:

1. Slide your assembled barrel group into the gun, pushing back on the retention lever to ensure it does not get in the way.
2. Open your feed tray cover.
3. Push a spare inner barrel or round object of similar diameter down the muzzle of the gun to in turn ensure that you have pushed the hop up chamber back against the engine.
4. Look down into the hole for the hop up chamber retention set screw and ensure that you can see the groove of the chamber through it. If you cannot, you have not pushed the chamber backwards enough.
5. Apply some thread lock to the set screw, the hole, or both.
6. Install and tighten the set screw using the 2mm driver.
7. Close the feed tray cover and allow the thread lock time to dry before firing the gun again