SG550

The SG550, also known as the Stgw 90 or PE 57, is a selective-fire rifle developed in Switzerland by the Swiss Arms AG company. It entered service with the Swiss Armed Forces in 1990, replacing the SIG SG 510. The SG550 is a gas-operated rifle chambered in 5.56x45mm NATO. It features a rotating bolt and a stamped steel receiver.

The rifle is known for its modular design, allowing for various attachments and configurations. It typically comes with a folding bipod and iron sights, but can be fitted with optical sights. The SG550 has a reputation for reliability and accuracy, making it a respected firearm. The Swiss military designation Stgw 90 translates to "Assault Rifle 90."

While primarily used by Switzerland, the SG550 and its variants have also seen export to several other countries. Different versions exist, including carbine and light machine gun configurations. The design incorporates features that enhance its usability in various environments and combat situations. Its distinctive muzzle brake and gas system contribute to its manageable recoil.