Later on, he hides a gun inside one, using the lens as a barrel extension.

These flaps engage the cuts made in the short barrel extension to provide rigid locking.

For even more muzzle energy, a folding barrel extension can increase the barrel length to 21 calibers.

It uses a locking ring, which is located at the end of the barrel extension, to lock the bolt.

M4 feedramps are extended from the barrel extension into the upper receiver.

The barrel's threading is 1/2-20 and allows a barrel extension to be attached.

It was mounted over the left action rod and supported by the barrel extension.

Adding the barrel extension makes it accurate up to thirty feet.

On firing, both the barrel and barrel extension recoil to the rear.

The extractor is mounted on the left side of the barrel extension.