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SIG556 Shorty

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PAGE 1: SIG556 Shorty

King Arms SIG556 Shorty is a full metal AEG replica of 5.56 x 45mm NATO cal. carbine, with a simulated breech movement - EBB.



SIG556 5.56 x 45mm NATO cal. carbine produced by SIG SAUER (SIG Arms Corporation), was introduced in 2006 as a firearm dedicated to legal enforcement powers and civilians, targeting mainly US market. It is based on SIG SG550 assault rifle with altered to meet American customers needs. So there is a M4 type stock and RIS on handguard.


SIG SAUER firearms have a number of fans all over the world. SIG rifle and short versions are being modified so you may find number of customs - especially in the USA. To meet the market demand, producer decided to release SIG556 SBR (Short Barrel Rifle), offered in number of different configurations: with M4 stock or Magpul CTR (with a solid run and as well folded sideways) but as well without a stock - so called SIG556 Pistol.



In the same way SIG556 Shorty came out and King Arms made its replica. SIG SAUER catalogue for 2009 offers SIG556 Short and as well P556 SWAT without a stock.




Traditionally King Arms replica is packed in a solid cardboard box which ensures of safe transportation.



As always there is the KA neat design in black-red with a large logo. Box is filled with a stiff foam material which protects the replica and all the accessories. Same material cover (15mm thick)  protects also the front of the box.


In the box apart from the replica itself you will find a 135BB mid cap, transparent quick loading tool, Tango Down handguard vertical pull (RIS type) and a manual. Quick loading tool has also an attachment for pistol mag loading.


Manual is in English, there are clear pictures explaining maintanance. There is also a simple leaflet showing how to connect the battery.





From the very beginning replica feels solid, which we have already accustomed to as far as King Arms is concerned. High quality matches the good balance and parts feel well matched together.


All the parts have no unwanted play except for the stock. Both RIS hangguard and pistol grip are well fit with the body. Only when intentionally pressed you may feel a bit of play in the top of a RIS handguard on the connection with the body. Nevertheless it is minimal and it does not affect the usage.


Pistol grip similarily as the stock is made of nylon and feels solid - there is no unwanted sound or play. It is similar in look to those in M249 replicas. As it is expected in a modern replica it is handy and comfortable.


M4 type tactical stock has six settings, though there is a bit too big difference in diameter between stock and the guide tube on which the stock is set. It results in some play, which is much more noticeable than other M4 stocks we had a chance to compare. But it neither doesn't affect the usage.


Stock foot is made of comfortable rubber.


Both sides fire mode selector works smooth with a silent "click", but the moment when it stops on the selection is not that easy to feel. It is easy to skip to the next setting. In the "safe" mode you might feel a bit of play on the piston.


Even though it is said to be compact "Shorty" it is surprisingly heavy which improves the "real" climate and makes it feels solid and firm. The firm feeling is even better thanks to a short vertical RIS grip (Tango Down).




Replica looks really nice. Again it resembles the real SIG very well. Metal parts and those made of ABS are in the same mat tint - from lead black to deep black. Body and front of the replica precisely resemble the real gun. Mat parts are cold on touch and it gives a nice "real" feeling. On the left side of the body, there are two spots, which we suppose are in the location where protruding metal from the mould were cut off.


Metal parts of the replica are made of aluminium. Flash hider is made of steel, which we have checked with magnet test.


Sights are very simple. Muzzle is being folded horizontally to the rear. There is a sideways adjustment possible.


A see-through type rear sight is a thin plate adjustable vertically, it hides fully in the cut in of upper RIS rail. It is not easy to take it out without any tools, since it is hidden pretty deep in the rail. The reason to character and a simplicity of the carbine sights is that it is designed to work with optical sights (like collimator).


Front handguard has also a sideways folding stock latch. So there is a possibility to replace the stock with the one folded sideways to the front.



Replica has SIG ARMS INC. USA licensed marks. There are no additional marks which would not be same with a real firearm. On the left side of the body, there are calliber marks and producer name. On the same side a bit below, there is a serial number.


Fire mode selector has marks: S (for safe) and F (for fire). First selection between S and F switches to semi-auto mode. Second selection, right on the F mark, switches to fully automatic.


On the right side of the body, there are same fire mode marks and serial number on the breech.


Four RIS rails have numerical marks made with a clear white font.




Replica works with a battery dedicated for such a stock. This is 1400mAh battery which have cells connected like in stick battery though in two rows. To get to the battery, remove the rubber stock foot, unscrew one small screw and pull the clip where battery is placed.



There is also an option to use LiPo battery in the guide tube of the stock.



Mini type connector.





To take the replica apart remove one pin in the front, and unscrew two Allen screws (below the magazine socket). Then push upper body to the front, and pull it up.

Taking out the pin allows also to disassemble handguard. Slide lower part of the handguard to the rear and take it off by pulling down. Upper part of the handguard may be taken out after removing Allen screw (in the front). Unfortunately while taking apart front of the handguard lower part scratches a bit lower body.



1. Gearbox

GB is not standard, based on v.3, though with a "residuary" engine socket.


In the upper part, gearbox has a cut in for EBB system (Electric Blow-back).


Fire mode selector mechanism and its plate are also not standard.


Fire mode selector racks, have marks (rectangular nub), which have to be in the same position on the both gearbox sides.


EBB module connected with reload handle. Module is located in the upper part of the body.


Nozzle is a bit longer than a standard one.


Gearbox have 7mm steel racks with a bit too much play and in our opinion they require better washers. Piston rack has additional gear sector clip which is responsible for pusher delay which is literalily keeping the nozzle in the back a bit longer. It improves feeding BBs into HU chamber, especially with a high rate of fire.


Cylinder is type zero, which is surprising regarding barrel lenght.


Piston is adapted for electric blow back simulation by a small cut in. Some tear down shreds are visible as a result of EBB system. Two cogs were already preety worn down. We have also found some plastic filings inside the gearbox which might have been a result of EBB systemor just racks working with a piston. "Syringe" test was positive, proving good tightness of a cylinder set.


2. HU chamber


HU chamber is standard for King Arms with their extention which is works with an untypicaly long nozzle. Inner barrel is 233mm long.




Mid cap which is found in the box has capacity of 135 BB. It is made of black plastic. Surface is mat and a bit rough. On sides it has rails which along with a dedicated clip helps to connect mags together.


On the low left end there is a producer logo: SIG ARMS.



Mag fits with a bit of sideways play, but in general it fits firm and after releasing a catch it falls out smoothly. During our tests mag was feeding BBs without any failure or blank shots.


M4/M16 mags of some producers would also work. All of those which are usable, fit pretty tight in the socket, there is no play and they feed BBs without a failure.


ICS metal hi-cap (450BB capacity):


Chinese metal hi-cap  (400BB capacity), sold under the brand of P&J:


Chinese metal hi-cap (190BB capacity) [short plastic real caps will not fit!]:


G&P metal mid cap (130BB capacity):



M4/M16 mags: MagPul PTS PMAG, MAG mid caps and real caps P&J will not fit!



There is a breech simulation system EBB which is visually nice, but you will almost not feel any difference while shooting. It improves the general "real" climate though it is worth reminding that the system is quite vulnerable and if suddenly blocked it may even result in gearbox damage - which is even mentioned by a producer. Breech movement is short - around 15 to 20mm.

Simplicity not to say primitiveness of mechanical sights would rather mean that they would be used as a last ditch aiming device. To aim accurately it would require optical sights or other sights mounted on RIS.

Gearbox performance was not that good as we presumed, there was a noticeable rasping sound of racks. Our first thought was that it might be the engine setting, but getting it adjusted didn't solve the problem. After disassemble and reassemble of the gearbox with washers adjustments, the performance improved: replica was working well, and the sound was correct.

We had some problems with HU adjustment. It resulted in pretty bad recurrence test results - especially with 0.2g BB. Hop-up had not added enough spin. With 0.25g BB results were better but still there were single shots which couldn't reach avarage distance. According to our experience with KA replicas we would suggest replacing HU rubber. Probably it might also help if inner barrel would be replaced with precise version.



We have used 0.2g and 0.25g BB (Blaster and ICS).


1. Muzzle velocity and energy


Muzzle velocity was measured with MadBull Revolution Ver.I chronometer and 0.2g BB.


Avarage muzzle velocity for KA SIG556 Shorty with 0.2g BB is 345fps while energy 1.05J


Results are math avarage values, hi-low difference was 19fps.


BB weight | fps  | m/s | energy

0,2g         | 345 | 105 | 1,05 J


2. Rate of fire

RoF was measured with 10.8V battery and 0.2g BB. It is 11 shots / second.


3. Accuracy and convergence in the distance of 20 and 30 meters.


Test was performed on the sillhouette target with an A4 piece of paper in the centre. Distance was set with a measure tape. Shots taken in the series of 10.


Shooting tests were performed with 0.2g and 0.25g BB.


With 0.2g BB in the distance of 20 meters, we had 9/10 hits in silhouette from which 4 in A4. Margin hits in the range of 190mm, 3 closest hits in 75mm diameter circle.



In the distance of 30 meters, 3/10 in sillhouette.


For 0.25g BB in the distance of 20 meters 10/10 shots in sillhouette from which 9/10 in A4. Margin hits in the range of 240mm, while 3 closest hits in 50mm diameter circle.



In the distance of 30 meters 6/10 shots in sillhouette.


4. Maximum and effective range.

Effective range is around 20 meters. In this range 10/10 shots hit sillhouette. Maximum range is around 30 meters.


King Arms SIG556 Shorty is another replica which is very good looking with high quality of outer parts. Good resemblance of a real gun and original marks are improving visual attractiveness of this model.

As far as outer parts quality is high-end we claim that KA inner parts might need some improvement.

In our opinion, stock SIG556 Shorty would be useful in short range and compact size would predestine it for CQB games and it should work well there.

For those who would decide for tune up with inner parts replacement, SIG556 Shorty, thanks to high quality of outer parts,  might be a nice base to build a very good replica.



Replica tested thanks to courtesy of KING ARMS, SIG556 Shorty producer:



Real gun photos:

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