SIG-Sauer 516 Sport

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Introduced at the 2010 Shot Show, the 516 rifle from SIG-Sauer is today available in a variety of configurations, both in civilian legal semiautomatic configuration and military / law enforcement restricted selective fire models. Chambered in .223 Remington and 7.62x39 Russian, the 516 rifle also spawned a “big brother”, the 716, chambered in .308 Winchester / 7.62x51mm NATO.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The muzzle of the SIG-Sauer 516 carbine features a standard birdcage flash hider

The 516 rifle is based on the classical AR-15 platform template, improved and enriched with a series of design features, the most important being the introduction of a gas operated, short stroke piston and push rod system, with a completely redesigned bolt carrier group.

The design retains many existing “standard” parts and measurements, to maintain a measure of compatibility versus other AR based products – the whole piston operated upper receiver is, in fact, available as a complete drop in part from the manufacturer to upgrade a customer’s own AR-15 rifle to SIG-Sauer’s improved system. 

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The front sight base is replaced by a gas unit which houses the short stroke piston and is topped by a short Picatinny rail. Note the bayonet lug

Initially only available in the United States, the 516 has since been also manufactured in Germany for the European market, and is available in the “Old Continent” for purchase in select configurations.

The 516 configuration we feature in our review is the civilian legal, semiautomatic Sport “Patrol” model, chambered in .223 Remington.

For legal issues in those European countries where the length of the barrel must be at least 420 mm to be considered “sporting”, as in Germany, the barrel of the 516 Sport is 16,6” long and features a standard 0.5x28TPI muzzle threading, accommodating a classic birdcage flash hider, which can be easily replaced with many aftermarket muzzle attachments, brakes or flash suppressors.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The 516's ejection port with door is 100% AR-15 standard in shape and size, insuring extremely reliable ejection and cycling...
SIG-Sauer 516 semiautomatic carbine in .223 caliber
...while the bolt carrier group is completely proprietary, lacking gas relief ports. Note the "zivil" engraving, immediately recognizable as a civilian part

The profile of the cold hammered forged barrel is optimized for accuracy, being medium heavy; it features a 6 groove rifling with a fast 1:7” twist, and the bore is chromed for long life.

The barrel is matte black nitride finished for excellent corrosion resistance, and is totally free floated in the proprietary railed handguard.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The 7075-T6 alloy handguard with Picatinny rails features sling mounting points for standard push button release connectors

The front sight base on the barrel is replaced with the proprietary gas block, which houses the adjustable, four position gas regulating valve.

The operating rod assembly includes the guide and spring, and uses an inverted piston, in which the “spigot” portion of the regulating valve injects the gas inside the op-rod, which doubles as a gas cylinder.

Excess gas is vented through a series of holes around the cylinder, and a series of three small gas rings on the tip of the spigot insure reliability and proper operation cycle.

The gas block does also feature a standard bayonet lug, although the non-standard length of the barrel in front of the block prevents the bayonet ring to engage the flash hider. 

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The SIG-Sauer 516 semiautomatic carbine in our brief live fire test. In some European markets, the Magpul stock and grip is replaced by FAB Defense products; the folding "iron" sights mounted on the firearms are a set of ARMS Polymer #71L BUIS, while the optical sight is an Aimpoint Micro T1 with an American Defense lever lock mount
SIG-Sauer 516 semiautomatic carbine in .223 caliber
The SIG-Sauer 516 has a standard bolt assist and "T" handle as well.

One of the 516’s strong points is the fully machined, 7075-T6 aluminum alloy, railed fore end. Built using an upper and lower “shell”, that are fastened to the upper receiver using a series of hex bolts to form a very reliable and stable system, and the end result is that the whole assembly, for all practical purposes, works just as a monolithic upper; the barrel is free floated, and the only point of contact are the three gas rings in the gas cylinder/op rod, which in turn is housed in the upper portion of the handguard.

The handguard features four sling mounting points for standard push button release connectors, two on each side at both ends of the Picatinny rails. All slots are numbered for easy repositioning of optics and accessories.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
On the left side of the receivers, the usual AR type firearms controls are all easily operated by the shooter

The upper receiver is a beefed up but otherwise apparently standard “flat top”, with a few internal modifications to house the completely proprietary bolt carrier group, and an indexing notch machined in the forward end of the top rail to properly  align the railed fore end and push op-rod system.

The upper features a standard bolt assist control and spent case deflector.

The heart of the 516 is the beautifully finished bolt carrier, with integral piston impingement key. Manufactured from CNC machined steel billet, the bolt carrier features a frictionless finish and a specially designed geometry, to improve cycling, reliability and the different receiver wear pattern that is due to the off center vector imparted by the short stroke piston operation that pushes the bolt carrier group rearwards during fire, vs. the perfectly coaxial vector of the direct gas system of the conventional AR15 – what is conventionally called “carrier tilt wear”.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The MOE (Magpul Original Equipment) pistol grip with accessory compartment
SIG-Sauer 516 semiautomatic carbine in .223 caliber
The very sturdy and reliable Magpul MOE collapsible stock mounted on the 516 rifle

The bolt used is a standard, milspec part, down to the use of gas rings on the bolt tail, which are now only needed to increase drag within the BCG; the same goes for the cam pin and firing pin.

The version of the SIG-Sauer 516 Patrol rifle we tested used a standard lower receiver, instead of the more feature rich US version, that sports a custom designed lower with machined ambidextrous sling mounting points for standard push button release connectors on the rear portion of the receiver and various other improvements including a spring loaded system to limit play between the upper and lower receivers.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The railed handguard on the SIG-Sauer 516 carbine is manufactured in the same 7075-T6 alloy as the receivers of the firearm, while the gas block that houses the "inverted" short stroke piston and op rod is carbon steel
SIG-Sauer 516 semiautomatic carbine in .223 caliber
SIG-Sauer 516 semiautomatic carbine in .223 caliber: left side view
Sig-Sauer 516 semiautomatic carbine in .223 caliber
SIG-Sauer 516 semiautomatic carbine in .223 caliber: right side view

The pin location and interface geometry between lower and upper of the 516 rifle is totally standard, and it is possible to exchange uppers; as previously stated above, SIG-Sauer actually offers a complete 516 upper receiver assembly for sale to update existing AR15 rifles to its own gas piston operated system.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The SIG-Sauer 516 rifle field stripped

The package is completed with a Magpul MOE (Magpul Original Equipment) collapsible stock and pistol grip, which is replaced in some markets with FAB Defense products. The same goes with the magazine; in the US, the magazine is a 30 round Magpul PMAG, in Europe it is replaced by shorter 20 round (limited to 10 in some countries) OA-MAG, manufactured in Germany by Oberland Arms.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
The Bolt and BCG assembly stripped for cleaning; the bolt is 100% Mil Spec. Note the protrusion on top of the BCG that impinges on the op rod

Our opinion on the 516’s ergonomics and control placement follows our belief that the AR15 way back in the 1960’s set the standard reference by which every assault rifle should be compared to, in other words, it’s almost perfection.

On the down side, none of the controls are ambidextrous, and trigger pull could be better – the rifle we live fire tested had a creepy pull and “sticky” release.

During our brief live fire test at the range, we experienced a smooth shooting session, with absolutely no failures over hundreds of rounds fired across multiple shooters.

Handling is good, although the 516 is a bit muzzle heavy, it does help tame the mild muzzle flip during rapid fire drills.

SIG-Sauer 516 semiautomatic carbine in .223 caliber
Detail of the short stroke piston and op rod removed from the 516 rifle

Accuracy is excellent, and perceived recoil is different from a standard M4, it seems slightly sharper but also milder, although the latter may be due to the heavier weight of the rifle compared to our “plain jane”M4.

All in all, we have been favorably impressed by the SIG-Sauer 516 Sport Patrol.

Fit and finish is excellent, the materials used are first class and the rifle does give a feeling of ruggedness, reliability and accuracy. 

It is also worth noting that in the near future all production will be carried out in the United States, therefore all civilian 516 rifles will be “Made in USA” and imported in Europe. 

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