Sig SG 552 Model 3D

n 1998, the SG 552 Commando carbine was introduced. It has a shorter 226 mm (8.9 in) barrel (with an open, 3-prong flash suppressor) and gas tube, ventilated handguards and a redesigned bolt carrier group that was integrated with the piston rod to form a single moving assembly. The return mechanism has been moved to the rear of the receiver housing and its recoil spring is guided in a way analogous to the AK-47, on a steel guide rod (later models feature a polymer guide rod) resting against the lower receiver"s rear surface under tension of the compressed recoil spring. Like the SG 550/551, this model can accept rails and accessories enabling the use of optics. A long barrel version of the SG 552 known as the SG 552 LB incorporates a 346 mm (13.6 in) barrel designed to fire rifle grenades and mount a bayonet.