Based on SIG's SG 550, the SIG556xi utilizes a rotating bolt and adjustable gas piston operating system, plus gives you the choice of caliber, barrel length, handguard/stock configurations and lower receivers. Yep, this puppy's adaptable.
A removable barrel gives you the option to select the necessary length for your application.
Its interchangeable bolts can be swapped to any of three calibers — 5.56x45mm NATO, 300 Blackout, and 7.62x39mm. You can also quickly change out the non-serialized lower receiver, allowing the use of either AR-style STANAG or rock-and-lock AK-style mags. Only the SIG556xi upper receiver is serialized.
Polymer handguards accept all Magpul light and rail kits, while the aluminum and carbon fiber handguards accept 2”, 4”, and 6” M1913 rails. Barrels are available in 10”, 14.5”, and 16”.
The ambidextrous, SIG556xi features an ambi safety selector, magazine release and user swappable charging handle (right- or left-handed). Optional receiver end plates allow for the use of either AR receiver extension tubes and buttstocks or M1913 compatible stocks.
Thanks to a redesigned trigger package, the military and law enforcement versions of the SIG556xi are capable of full-auto fire in every caliber, including 7.62x39mm. The Russian lower has been thoroughly function tested with many available AK magazines, including US P.A.L.M.
– 3-position adjustable gas piston operating system with rotating bolt
– Swiss-style folding stock with removable cheek riser
– Ambidextrous controls
– Locking flip-up front and rear sights
– Polymer handguard (compatible with Magpul® MOE® accessories)
– Caliber convertible: 5.56 NATO / 7.62 x 39mm / 300 Blk
My Recommended Tactical Rifle Resources
Gun Digest Book of The Tactical Rifle