Sig Sauer SIG 556 5.56 NATO – Early JS-Prefix, 16.5" CHF Chrome-Lined Barrel, Folding/Telescoping Stock, AR-Magazine Compatible
This early-production SIG 556 pairs Swiss-inspired engineering with U.S. manufacturing. Built around a short-stroke gas piston and stamped-steel upper, it features a 16.5 inch cold-hammer-forged, chrome-lined barrel that is threaded 1/2×28. The JS-prefix serial places it in the first wave of commercial SIG 556 rifles, a run discontinued in 2016 and now increasingly attractive to collectors.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Excellent – clean, mirror finish, no signs of wear.
Rifling: Excellent – sharp lands and grooves.
Specific Condition Notes: The upper receiver displays brass markings and scattered scratches. The original muzzle device is not present.
What’s Included
- SIG 556 rifle with folding, six-position telescoping stock
- Hooded Swiss-style fixed front sight (installed)
- Flip-up rear iron sight (installed)
- 3 × 30-round polymer magazines
- 1 × 20-round polymer magazine
The SIG 556 retains the proven SG 550 two-position adjustable gas regulator and non-reciprocating right-side charging handle, giving shooters a clean-running action and easy manual of arms. Its stamped-steel upper and forged-aluminum lower keep weight manageable while preserving rigidity.
The cold-hammer-forged, chrome-lined barrel is built for durability and accuracy. A 1:7 twist rate stabilizes the full range of 5.56 NATO projectiles, and the 1/2×28 threads accept common muzzle devices or suppressor mounts.
Unlike its Swiss predecessor, this model accepts standard AR-15 magazines, broadening accessory options and simplifying logistics. The folding hinge at the rear of the receiver also allows users to swap stocks or braces suited to their needs.
Collectibility is boosted by the rifle’s early JS-prefix serial and its status within the discontinued SIG 556 line (2007–2016). These early examples capture the original design intent before later generational changes.