SIG Sauer SIG551-A1 Classic 5.56 NATO, Swiss Gray, 16 in Threaded Barrel, Folding Skeleton Stock, Upgraded Rotary Diopter
This U.S.-made SIG Sauer SIG551-A1 Classic stands out with its Swiss-gray finish, black polymer furniture, and 55x-series configuration. It features a long-stroke gas piston system with a two-position adjustable regulator, a folding skeletonized stock, and a 16-inch threaded barrel with the factory long multi-slot flash hider. An upgraded rotary diopter rear sight is installed on a long top rail section, adding precise, repeatable sighting to the classic 55x layout while maintaining compatibility with original Swiss 550-series rock-and-lock translucent magazines.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Overall Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: This firearm is in great shape. There are minor, superficial scratches and small blemishes present on exterior surfaces. The bore is clean and shiny.
What's Included
- 1x 30-round translucent polymer Swiss 55x-pattern rock-and-lock magazine
- Owner's manual
- Rotary diopter rear sight assembly on receiver top rail (installed) and protected front post
- Factory 55x-pattern long multi-slot flash hider (installed)
- Additional polymer ribbed handguard (Classic 55x pattern)
Built on the 55x series pattern, this SIG551-A1 Classic uses a proven long-stroke gas piston with a two-position adjustable regulator for reliable operation. The right-side reciprocating charging handle and ambidextrous safety deliver familiar 55x ergonomics with modern controls.
The rifle uses a stamped-steel upper mated to a molded polymer lower, finished in Swiss gray with black polymer furniture. It retains the classic ribbed polymer handguard with elongated vents and a folding, skeletonized polymer stock. Overall length is 37.0 inches with the stock open and 27.2 inches folded; length of pull is 13.0 inches. Unloaded weight is approximately 7.8 pounds.
The 16-inch barrel is threaded and paired with the factory 55x-pattern long multi-slot flash hider. A 1:7 twist supports a wide range of 5.56 NATO projectile weights. The rifle accepts original Swiss 550-series translucent rock-and-lock magazines and includes one 30-round example.
Upgrades include a rotary diopter rear sight installed on a long top rail section, offering precise sight picture options. The front sight is a protected post with a green-dot flip element, and the receiver rail provides a solid mounting surface across the top of the rifle.