I maintain that SigSauer should have gone with SG557, SG560, or SIG762 for the SIG556R line. These United States made 7.62x39mm SG551 based rifles utilize AK magazines and have the same general function and ergonomics of their Kalashnikov equivalents, with the added bonus of an ergonomic safety selector.
Other differences include the factory rail, forward return spring, comfortable folding stock, suppressor setting on the gas system, and a better trigger.
The gun shown however, is something different. This unique SIG556R Gen.II has had the barrel replaced with an unused chrome-lined “Yugo” RPK barrel made by Zastava of Serbia. The gas system was stretched out to the SG550 length with an SG550 handguard and bipod installed.
The firearm was finished with a “SIG Dark Gray” Cerakote finish to complete the proper look with the black furniture. The rifle shown belongs to a friend that is good at keeping me informed and covetous, I call it an SG550R.
The 7.62 X 39 is a terrible cartridge, even Russia has abandoned it. It is not accurate, it has no range, it’s heavy for its destructive power, and it’s filthy when mil-surp is used. I have two SIG 556 Classics and they both print 1 MOA. I have considered converting one of them to a 20″ barrel version, but, it’s not worth the expense when I could buy a match grade, 1 MOA, FAL (already have one of those too) for the price. Every military rifle I own is capable of 1 MOA with match ammo, 2 MOA with commercial ammo, and 2-1.2 MOA with mil-surp. My sub-MOA AR-15 SP1 makes 4″ patterns with Wolf mil-spec 55 grain steel case.
WHY would you ruin a perfectly good rifle by doing this ? It defies rationale !
Ask SIG-Sauer Inc. as this rifle started as a factory SIG556R which was a production 7.62x39mm. What was done here was improve upon the initial weapon not convert the caliber.