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    Cyma/Cybergun SIG 556 AEG


    Cyma/Cybergun SIG 556 AEG review by Booligan
    Discuss this review HERE
    Table of Contents:
    Basic Gun Information
    First impressions/Packaging
    Gun Specifications
    A few years ago, through a licensing agreement with Cybergun, Cyma had produced a SIG 556 AEG. There's not too much information out there about it, so today I'll be writing a review on this interesting AEG. As I mentioned before, it's been available for a year or so, so it's not the newest model out there, but it's still a pretty awesome AEG, especially for the money! Keep reading for more information!
    I obtained this rifle through Airsplat, who has it available HERE, priced at $199.99. For that price, you get a skirmish ready full metal AEG with unique features for this type of gun, including a retractable stock and the ability to use M4/16 magazines. It also includes a warranty against manufacturer defects, so you don't need to worry about getting a DOA gun. The gun arrived a few days after shipping using UPS Ground, Airsplat's free shipping option.
    Basic Gun Information:
    The SIG 556 is a rifle based on the 550/551/552 platform, with a few key changes. Normally, those rifles utilize a side folding stock as well as a proprietary magazine, but with the 556, a retractable M4 style stock is used as well as STANAG magazines, making the gun very easy to use if you already have a stockpile of AR mags. It also comes with a polymer railed handguard as well as a railed upper receiver for mounting optics. These make it very easy to modify and accessorize the gun to your liking.
    First impressions/Packaging:
    As with all Cybergun licensed guns, the 556 came in a nicely decorated full color box. Inside the box, a foam inner liner keeps the gun safe during shipping, and the outer decorations highlight the gun's performance figures. My first impression on pulling the gun out of the box was realizing how heavy this thing is. For a midsized rifle, this gun weighs a ton.
    From this point on, click on the thumbnails to view full size photos
    Along with the gun itself, the package includes two hi-cap magazines, a stick type battery, trickle charger, cleaning/unjamming rod, and a basic manual.
    Included stick battery
    Gun Specifications:
    Weight: 8.4 lbs
    Length: 33.75" – 36.5"
    Width: 2.75" at handguard
    Height: 9"
    Sight Radius: 18"
    LOP: 11.25" - 14"
    This gun is one of the more unique looking AEGs currently available, due to its mixture of elements from the normal SIG rifle series with AR features. It is a full metal replica, as the only components that aren't made of metal are the pistol grip, stock, and handguard. The parts that are polymer are made of a nylon polymer material that is extremely strong. The paint finish on the gun is matte black, giving it a very realistic appearance.
    External overview, left side
    Overview, right side
    The stock is a GLR16 type unit, complete with inner compartment for storing batteries for your accessories. It has a rubber butt pad that can be pulled down out of the way to access the compartment. The stock tube is metal and is threaded into the adapter at the rear of the receiver. It's an oddly configured stock tube, with five adjustment positions, only four of which are easily accessed.
    Stock retracted
    Stock extended
    Stock tube
    Battery compartment
    Moving forward, you'll hit the receiver, which is based on the traditional SIG 55X models and is quite narrow and relatively streamlined compared to traditional AR receivers. The lower receiver houses the majority of the fire controls with the upper housing the cocking handle and top rail.
    Receiver, right side
    Receiver, right side
    One of the benefits of this platform is the ambidextrous selector switch, making the gun easy to use by left or right handed shooters. The magazine release is an AR type unit that is located on the right side of the receiver. The only other functioning control is the bolt handle that can be pulled back exposing the hop-up adjuster.
    Right sided controls
    Cocking handle
    Bolt pulled back
    The pistol grip is a SAW type unit which is slightly oversized but very comfortable. There are large grooves on the sides to aid in keeping a solid grip on the gun. A screw at the bottom allows you to remove the grip to access the motor and remove the gearbox.
    Pistol grip
    Moving forward from the receiver, you'll hit the railed handguard that doubles as the battery housing. The rails are molded into the handguard and are not removable, however they are still relatively comfortable to hold without covers in place. The battery compartment is designed to fit an 8.4v stick pack, but you can fit a 9.6 or even 11.1v LiPo pack in there if you carefully position the wiring.
    Rail surfaces
    Moving forward from the handguard, you'll hit the faux gas block and outer barrel. The outer barrel is made of metal and is terminated in a 14mm- threaded muzzle. It is equipped with a birdcage type flashhider with an orange plastic ring glued in place.
    Outer barrel and gas block
    Aiming the 556 is accomplished using the included iron sights that are adjustable for elevation but not windage. The front is a fixed unit with a flip up component that would normally house the night sight. The rear is a small unit that flips up from the top rail and can be adjusted for elevation. The railed upper receiver lets you mount optics if you so desire.
    Front sight, large post
    Small post
    Rear sight folded
    Rear sight flipped up
    Top rail
    One of the benefits of the Cybergun licensing are the licensed trademarks sprinkled throughout the gun. On the upper receiver you will find laser engraved markings indicating the manufacturer and model number. You will also find SiGARMS markings on the pistol grip, stock, as well as on the magazines.
    Receiver markings
    The included magazines are specially designed hi-caps, made of plastic and with a unique locking design allowing you to stack them together. They hold about 350 rounds each, and the gun includes two magazines. Due to the shallow magwell, you can fit pretty much any standard AR magazine in this thing, including Pmags and some drum mags.
    Feeding end
    Winding wheel
    Clipped together
    Performance after a 500 round break-in period, using Airsplat .20g BBs, shot through a Madbull Chronograph is as follows:
    High FPS: 387.7 FPS
    Low FPS: 382.4 FPS
    Average FPS: 385.9 FPS
    Rate of fire using the included 8.4v battery is fairly low, in the 15-16 RPS range. With a higher output battery, you'll see mid 20s, easily. The stock motor is a torque unit, but it does allow some speed with the right battery.
    Range and accuracy are pretty good, largely thanks to the decent length of the inner barrel combined with the BAX hop-up system. With heavier weight ammo, Echo 1 .28g in my case, I was easily able to hit my torso sized target at 160' without issue. The hop-up is pretty responsive and holds its selected position really well.
    Now to the biggest issue with the SIG platform - ease of access to the internals. The narrow receiver makes it damn near impossible to access the gearbox without a LOT of SIG specific experience. The space constraints involved with fitting a gear driven ambidextrous selector system take its toll on accessibility. In fact, when they build these, they place the two halves of the receivers together around the gearbox and then permanently attach them. So, if you need to open up the gearbox of this thing, I hate to say it, but either have a spare body handy, as you may break the factory one, or take it to your local shop.
    That being said, I'll explain the guts of this thing as best as I can with what I have in front of me. The inner barrel is approximately AK length, and the barrel can be accessed with relative ease, only requiring the removal of four screws at the front of the receiver. This will allow the entire front assembly to slide out and off the gun. You can then pull the inner barrel out of the hop-up if you want to swap it out with a tightbore. The hop-up bucking uses a split nub design to give more consistent application of pressure to the BB. Part of the hop-up system is the long feed tube required with using AR mags in a SIG gun, and as a result, you lose about 10 BBs of capacity from your mag.
    Further disassembly entails removing the two screws at the rear of the receiver as well as removing the pistol grip. You can then separate the upper and lower halves, letting you access the gearbox somewhat. The issue with removing the gearbox lies with the design of the selector assembly. In order to pull the gearbox out of the receiver, you have to pry the lower section of the receiver away from the selector switch assembly in order to clear it. With a plastic bodied SIG, this is tricky, but still possible. With the metal body, especially a potmetal body like this, I bent it as far as I felt comfortable without cracking the receiver and still couldn't get the gearbox out. It's just a bad design, but it comes with the SIG territory. You can see the split in the clamshell receiver design where they literally build the gun around the gearbox, instead of just placing the gearbox inside once the body was built.
    Gearbox in lower receiver
    Steel bushings, close-up of motor half cage
    That being said, I can tell you that the gun uses a non-ported brass cylinder, steel bushings and gears, a V3 gearbox with cutout for a blowback system (but no blowback system itself), a polymer spring guide, and a polymer piston with ventilated head. A peek inside shows minimal lubrication, but I cannot comment on the shimming aside from saying that it sounds pretty good while shooting. Unfortunately, I don't feel comfortable diving deeper into the box to check air-seal, but I imagine that it's pretty good, especially considering the FPS consistency that I saw in my performance testing.
    As far as modifications go, you have many options due to the railed front end and M4 stock tube. You can swap out the stock with with different units, however, the gun requires a real-steel type buffer tube so mounting some full/adjustable stock units may be tricky. In my case, I'm setting it up as a DMR, complete with CTR stock, long eye relief optic, folding bipod, and some upcoming internal upgrades.
    Full metal construction
    Affordable price – Sub $200
    Very skirmishable performance
    Plenty of rails for accessories
    Utilizes AR magazines
    Adjustable stock fits most users
    Realistic weight
    Limited to stick type batteries
    Receiver paint finish is a little fragile
    Long selector switch travel
    Drops 10 or so BBs with every mag change
    Gearbox is damn near impossible to remove without breaking the body
    I've always been a fan of SIG type rifles, however I was always put off by the required proprietary magazines, as well as the non-adjustable stock. The 556 alleviates those concerns by allowing the use of AR mags, of which I have dozens, as well as the use of a collapsable stock, letting me adjust it to fit to my liking. It gives you all the functionality of an M4, but with a vastly different look and feel. I really like it, and I think with some slight tweaks, it'll make a decent little DMR platform.
    Many thanks again to Airsplat, and of course, Airsoft Retreat!