Manual

2.1.2 Barrel with receiver and gas system
The barrel is screwed into the receiver. The muzzle is fitted with a
flash suppressor. The front sight mount, which is fixed to the barrel,
contains the gas port, accepts the front sight and gas system and
also serves as a support for the handguard.
The receiver guides the bolt and houses the locking system.
The rear sight mount with diopter drum is also mounted on top of
the receiver.
Barrel with upper receiver and gas system
1. Flash suppressor
2. Barrel
3. Gas valve
4. Front sight
5. Gas piston
6. Recoil spring
7. Gas tube
8. Rear sight mount
9. Diopter drum
10.Receiver casing
11.Front sight mount
12.Bayonet lug (on SG 550 only)
5