SIG 516
SIG Sauer · Carbine · In Production · 2010
Also known as: SIG Sauer SIG516, SIG SG 516, Sturmgewehr Model 516
Overview
The SIG Sauer 516 is a premium AR-15 variant featuring a short-stroke gas piston operating system, introduced at the 2010 SHOT Show as SIG Sauer's flagship rifle platform. Designed by principal firearms engineers Robert Hirt (formerly of Heckler & Koch who worked on the HK416) and Chris Sirois, the 516 represents an improved evolution of piston-driven AR designs. The standard Patrol model features a 16-inch cold-hammer-forged, chrome-lined, nitride-treated barrel with a 1:7 twist rate optimized for heavier 5.56mm projectiles. Weighing 7.3 pounds empty, the rifle utilizes a proprietary short-stroke push-rod piston system that keeps propellant gases and carbon fouling out of the action, allowing the rifle to run significantly cooler and cleaner than traditional direct impingement AR-15s. A distinctive four-position gas regulator allows users to tune gas flow for different ammunition types, suppressor use, and environmental conditions. The forged 7075-T6 aluminum upper and lower receivers feature hard-coat anodized finish, with the flat-top upper providing a full-length Picatinny rail. The rifle comes equipped with free-floating handguard, folding backup iron sights, six-position telescoping stock, and fully ambidextrous controls including magazine release, bolt catch, safety selector, and charging handle (on Gen 2 and later models). The 516 accepts all standard STANAG magazines in 5-, 10-, 20-, and 30-round capacities. Later generations introduced improved handguard designs with M-LOK mounting, enhanced internal components including steel cam pathway reinforcements and feed ramps, and the SIG Matchlite DUO trigger.
Specifications
| Weight (empty) | 3311 g (116.8 oz) |
| Weight (loaded) | 3881 g (136.9 oz) |
| Overall Length | 914 mm (35.98") |
| Barrel Length | 406 mm (15.98") |
| Sight Radius | 356 mm (14.02") |
| Action Type | Gas Operated Short Stroke Piston |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Trigger Pull | 34 N (7.6 lbf) |
| Magazine Capacity | 30 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 905 m/s (2969 fps) |
| Muzzle Energy | 1640 J (1210 ft·lbf) |
| Effective Range | 500 m (547 yd) |
| Maximum Range | 3600 m (3937 yd) |
| Barrel Rifling | Right Hand |
| Rifling Twist | 178 mm (7.01") |
| Number of Grooves | 6 |
| Frame Material | Aluminum Alloy |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Hard Anodized |
Calibers
- 5.56x45mm NATO · primary · 5.56x45mm NATO — also known as 5.56mm NATO, 5.56x45mm, .223 Remington
Features
- Firing modes: Semi Automatic
- Feed systems: Detachable Box Magazine
- Safety mechanisms: Manual Safety Selector, Four Position Gas Regulator
- Features: Short Stroke Piston System, Four Position Gas Regulator, Rotating Bolt, Flat Top Receiver, Picatinny Rail, M4 Feed Ramps, Forward Assist, Dust Cover, Cold Hammer Forged Barrel, Chrome Lined Barrel, Nitride Treated Barrel, Free Float Handguard, A2 Flash Hider, Folding Sights, Six Position Stock, Ambidextrous Controls, Quick Release Sling Mounts
Variants
- SIG 516 Patrol — Standard
- SIG 516 CQB — Short Barrel
- SIG 516 PDW — Personal Defense
- SIG 516 Precision Marksman — Designated Marksman
- SIG 516 Gen 2 — Improved
- SIG 516 G3 MOHAWK — Latest Generation
- SIG 516 Russian — Chambering Variant
Service history
Operators
- Delaware State Police · adopted 2012
- Cincinnati Police Department SWAT · adopted 2012 · as SIG 516 CQB
- Florida Highway Patrol · adopted 2019
- San Diego Police Department SWAT
- Anderson County Sheriff's Office SWAT
- Indonesian Mobile Brigade (Brimob) · as SIG 516 Patrol
- Indonesian National Armed Forces Special Operations · as SIG 716 G2
- Turkish Police Special Operation Department (PÖH) · as SIG 516 Patrol
- UK Metropolitan Police Counter Terrorist Specialist Firearms Officers
- Civilian Sport Shooters
Production
Production years: 2010-present
Continuous production with multiple generation updates (Gen 1, Gen 2, G3). Available in multiple variants including Patrol, CQB, PDW, and Precision Marksman configurations.
Origin
Country of origin: United States
Designer: Robert Hirt, Chris Sirois
Notes
The SIG 516's development lineage traces directly to the HK416 through Robert Hirt's involvement, though SIG engineers implemented numerous improvements to address ergonomic and maintenance issues present in earlier piston AR designs. The four-position gas regulator (normal, adverse, suppressed, and off) provides exceptional versatility, with the 'off' position allowing the rifle to function as a straight-pull bolt action for ultra-quiet operation or manual cycling. The short-stroke piston system eliminates the reciprocating mass issues of long-stroke pistons while avoiding the carrier tilt problems that plagued some early piston AR conversions. Unlike direct impingement ARs where hot gases blow back through the carrier key into the action, the 516's piston system vents gases at the gas block, keeping the bolt carrier group substantially cooler and cleaner. This design philosophy prioritizes reliability in adverse conditions, extended firing schedules, and suppressed use. The rifle's weight penalty (approximately 1 pound heavier than DI ARs) results from the piston assembly and more robust construction. The 1:7 twist rate stabilizes bullets from 55 to 77 grains and handles long-range precision loads well. Gen 2 models introduced easier disassembly of the piston system, addressing early complaints about maintenance complexity. The G3 MOHAWK (announced 2025) represents the current evolution with MCX-derived features, non-reciprocating side charging handle, full ambidextrous controls, and improved M-LOK handguard replacing earlier quad-rail designs. A 7.62x39mm variant (516 Russian) offers ammunition commonality in certain markets. The 516's adoption by multiple law enforcement agencies validates its reliability, though its premium pricing (typically $1,800-2,200) limits widespread military adoption. Suppressor users particularly appreciate the cleaner-running piston system and adjustable gas settings.
Background
When SIG Sauer unveiled the 516 at 2010 SHOT Show, it entered an increasingly crowded market of piston-driven AR-15 alternatives including the HK416, LWRCI M6, and POF P415. The rifle's HK416 heritage through Robert Hirt's design leadership immediately drew comparisons, with firearms enthusiasts noting both similarities and improvements. Early adopters praised the four-position gas regulator as superior to competitors' simpler two-position systems, particularly for suppressor use which was rapidly gaining popularity among civilian shooters and law enforcement. The 516's selection by Delaware State Police in 2012 marked an early validation, followed by Cincinnati SWAT's choice of the CQB variant to replace 9mm submachine guns. These law enforcement adoptions highlighted the 516's perceived reliability advantages over traditional AR-15s, particularly for agencies concerned about weapon maintenance during extended operations. Turkish special police adoption further demonstrated international appeal. However, the 516 faced criticism from AR purists who argued that Eugene Stoner's direct impingement design, when properly maintained, offered superior accuracy due to fewer moving parts affecting barrel harmonics. The rifle earned a reputation as an excellent choice for suppressor users, with many noting dramatically reduced gas blowback compared to DI ARs. Internet forums debated endlessly whether the piston system's advantages justified the weight penalty and higher cost. The G3 MOHAWK's introduction in 2025 showed SIG's commitment to continuous improvement, incorporating lessons learned from the MCX platform. Today, the 516 occupies a premium niche-respected by professionals and enthusiasts who prioritize reliability over weight savings, appreciated by suppressor users for its cleaner operation, but remaining a minority choice in the AR-15 world where traditional DI guns dominate through lower cost and lighter weight.