Geissele Super Duty SD-556 5.56 NATO, 16 Inch, Two-Tone (Black Receivers/DDC MK16 Rail), Super Mid-Length Gas, Geissele Trigger
The Geissele Automatics Super Duty SD-556 stands out for its duty-grade build, two-tone finish with black Type III hard-coat anodized receivers and a DDC MK16 M-LOK handguard, and proven Super Mid-Length gas system. This rifle features a 16-inch cold hammer forged, chrome-lined barrel with a 1:7 twist, a Reliability Enhanced BCG with Nanoweapon coating, and a Geissele Trigger. The free-float MK16 M-LOK handguard is T-marked and carries NSN 1005-01-684-7293, underscoring its professional pedigree. This example is in excellent condition with minimal signs of prior handling.
Condition
Overall Condition: Excellent condition, showing only faint signs of any prior use or handling.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Notes: Only minimal handling marks are present. Surfaces appear clean throughout. See photos for close-ups.
What’s Included
- Geissele Automatics Super Duty SD-556 rifle
- 1x 30-round Magpul PMAG GEN M3 5.56 AR/M4 magazine with window
- B5 Systems vertical foregrip (installed)
- M-LOK QD sling mount (installed on handguard)
- Short M-LOK Picatinny accessory rail section (installed on handguard underside)
This Super Duty SD-556 is built around a 16-inch, cold hammer forged, chrome-lined barrel with a 1:7 twist for 5.56 NATO. The barrel is threaded and capped with a closed-tine flash hider/compensator, offering practical muzzle control and compatibility with common accessories. The Super Mid-Length gas system pairs with a Geissele Super Compact Gas Block for smooth, consistent cycling.
The rifle uses Geissele’s Reliability Enhanced BCG treated with their Nanoweapon coating for durability and ease of maintenance. An Airborne Charging Handle provides ambidextrous control, and an ambidextrous bolt catch/release with a maritime-style bolt catch enhances manipulation from either side.
A free-float Geissele Super Modular Rail MK16 in DDC provides a rigid, M-LOK accessory interface. The top rail is T-marked and bears NSN 1005-01-684-7293. Installed accessories include a B5 Systems vertical foregrip, an M-LOK QD sling mount, and a short M-LOK Picatinny rail section to support common attachments.
The upper and lower receivers feature a black Type III hard-coat anodized finish. The lower receiver is roll-marked GEISSELE AUTOMATICS, model SD-556, CAL 5.56MM; the upper receiver is plain with no such roll marks. Furniture includes an adjustable, collapsible tan stock and a B5 Systems tan pistol grip. A Geissele Trigger rounds out the fire control, delivering the crisp, dependable break that Geissele is known for.
This AR-15 platform rifle is a semi-automatic, direct impingement design with a measured length of pull of 14.0 inches. Capacity is 30+1 with the included PMAG. Made in the USA.