The gas system can be disassembled without requiring a full breakdown of the rifle. To remove the gas piston rod, the gas regulator must be unscrewed and removed from the front of the gas block. It does not employ an interrupted thread system, so it must be fully unscrewed. The steel gas piston rod is a one piece unit with a matte-gray, corrosion-resistant coating. It features a return spring assembly and dual gas vents on its forward portion.

The rear of the gas piston is designed to impact directly against the bolt carrier assembly, so the SIG516’s bolt carrier features an integral strike plate in place of a traditional gas key. This is the portion of the bolt carrier against which the rear of the piston impacts. The rear of the carrier has raised radial ridges designed to reduce friction between the carrier and lower receiver extension. Additionally, it provides greater reliability under adverse conditions because dirt, dust and sand can enter and not increase friction as with a perfectly concentric carrier. The bolt dispenses with the gas rings of a traditional AR system. The SIG516 does, however, feature an AR buffer system, and the buffer tube is designed to military rather than commercial specs.

Close Up
In its general configuration, the SIG516 Patrol is a flat-top AR carbine with a 16" barrel. The 7075-T6 forged aluminum A3-style flat-top upper receiver features the traditional forward assist and shell deflector, and it mates directly with the top rail of the carbine’s free-floated, four-rail fore-end as well as a strip of Picatinny rail on the top of the gas block. This provides users an uninterrupted strip of Picatinny rail along the entire upper length of the carbine.

The fore-end is an aluminum, SIG Sauer-branded Troy Industries MRF BattleRail unit free-floated around the barrel. The chrome-lined barrel, sporting the now seemingly standard M4-style contour, is fitted with a Yankee Hill Machine Co. Phantom flash suppressor.

The lower receiver, also of forged 7075-T6, sports unique cosmetic and ergonomic enhancements. The fence around the magazine release button on the right side of the lower is more pronounced than that of a standard AR, and the front face of the magazine well is checkered for enhanced purchase by the support hand. The left side of the lower receiver has a channel forward of the bolt catch to help prevent marring of the receiver during disassembly, and the mouth of the magazine well features a generous chamfer.

Further enhancements include a Magpul MIAD modular pistol grip and a Lewis Machine & Tool SOPMOD enhanced six-position buttstock. The pistol grip is customizable to a variety of hand sizes, and the buttstock sports a padded buttplate and enlarged cheek-weld sections that double as watertight battery storage compartments.

Hands On
Shortly after my visit to Exeter, my test SIG516 Patrol arrived. Once I had the rifle, I gave it a quick once-over, cleaning and lube, mounted a Leupold Mark 4 CQ/T optic and headed to the range with a sampling of .223 Rem. and 5.56x45 mm NATO ammunition.

I tested it for functioning and accuracy with three types of ammunition. The Patrol proved to be extremely pleasant to shoot, with a gentle recoil impulse. The two-stage trigger was excellent, breaking cleanly at 3 lbs. and making the SIG516 Patrol quite easy to shoot well. And shoot well it did, averaging roughly 1½" at 100 yds. overall with all three ammunition types and some Black Hills groups measuring less than 1 m.o.a. In addition, during the course of the few hundred rounds fired, I did not have a single malfunction with the carbine.

Once all was said and done, the SIG516 struck me as being exactly what SIG Sauer had intended: an enhanced AR that addresses the design’s perceived weak points while retaining all of its positive characteristics. The rifle was a pleasure to shoot, was accurate and appears to be undeniably reliable.

And, this is not the only offering planned for the series. In addition to more SIG516 5.56x45 mm NATO offerings, there are plans to introduce a variant in 7.62x51 mm NATO as well.

In my opinion, the SIG516 and its subsequent siblings portend great things for the future of the long-lived AR-style rifle, combining American know-how with precision European engineering—all in a tough and reliable package.