| | Modern Firearms - Assault Rifles - SIG SG-550 SG-551 SG-552 Stgw.90 |
 | | SIG 550 had been derived from previous model SIG 540 and SIG 541, and was adopted as a Stgw.90 assault rifle in 1983, but due to financial reasons production began only in 1986. |
 | | Version of the 551, called SIG 551 SWAT, is intended for law enforcement and is equipped with acessory rails on the forearm and comes with Trijicon ACOG optical sight and cheekpad on the buttstock. |
 | | Due to the short barrel and resulting short gas piston rod, the main spring in SG-552 was relocated to the receiver, behind the bolt carrier group, so the bolt carrier of the SG-552 is not 100% similar to the bolt carriers of the SG-550 and 551. |
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