ARMOURY: SIG MPX

MISSION

CRITICAL

SIG HAVE REALLY UPPED THE ANTE WHEN IT COMES TO CREATING AEGS AND GBBS THAT ARE NOT ONLY DESIGNED FOR AIRSOFT PLAY, BUT ALSO FOR REAL-WORLD TRAINING APPLICATIONS UNDER THE SIG AIR BANNER, AND THEY’VE WORKED WITH SOME PRETTY COOL NAMES IN THE AIRSOFT INDUSTRY ALREADY TO MAKE THIS HAPPEN! TO KICK OFF A WHOLE NEW YEAR OF AIRSOFT BOYCIE AND DAN GET UNDER THE SKIN OF THE VERY LATEST MODEL TO JOIN THE LINE, THE MPX!

At Shot Show 2015, SIG SAUER released their new rifle in the form of the MCX. This was designed as a modular, mission adaptable rifle based around the 5.56mm and .300 Blackout calibres which use the same receiver set, bolt and grips the user could configure the rifle to suit almost any mission they were to go on. Also, by changing the bolt, barrel and magazines the user could then build a 7.62 x 39 rifle.

The MPX,

which was designed in 2013 and released in 2015, was a contender to the replace the venerable yet ageing

MP5. The MPX though was to be available in 9mm, .357 SIG and .40 S&W calibres. Firing from a closed rotating bolt there are two main versions which are available from SIG. The Submachine Gun (safe, semi and auto version) is only available to Military and Police units, and the semionly version is available to the civilian market and where the local laws allow.

Using the same short stroke gas operated system as the MCX gives the user a safer and more reliable system as it fires from a closed, locked bolt. Utilising a 10, 20 or 30 round magazine it can cater for many applications. The semi only variant of the MPX is finding its way into the Pistol Calibre Carbine competitions around the world, most notably in the hands of Lena Miculek, who is a World Champion PCC shooter, member of the SIG SAUER Factory Team and uses the MPX PCC to great effect. Despite the COVID 19 problems around the world for the past two years VFC, the OEM, have been quietly working on the airsoft AEG version of the MPX and in November 2021 it was released to public sale in the Far East. This was quite a surprise to a lot of airsofters who had been asking for one for a long time but were not expecting it to actually become available for sale just yet. Airsoft Action have been really lucky to get hold of not one but two MPX to review and test over the coming months and I’m sure that Red Cell will be clamouring to get their hands on one of them at our regular test days. The one downside to the MPX release at the time of writing is that spare proprietary magazines are not yet available but with the advantage of having two AEGs, is that at least we can complete full magazine change drills as part of the testing.

FIRST LOOK

On opening the box, alongside the rifle and magazine is a nicely laid out manual and a pistol magazine sized speed loader with enough capacity to fill the magazine. When you look at the SIG AIR MPX the first thing that stands out to me is the build quality of the external parts. This is what you would normally expect from VFC, who OEM for SIG AIR, and they have produced a really lovely looking Pistol Calibre Carbine. Also, as this is an official SIG AIR product it carries all of the appropriate trademarks.

The lower receiver is almost identical to that of the MCX but with the obvious difference of the magazine well which is made to take the 9mm style magazine. The controls on the MPX are the same as the MCX, so will feel very familiar to MCX owners. The upper receiver is clearly different to that of the MPX and is not cross compatible with the MCX. Atop the receiver is the same ‘scooped’ Picatinny rail as the MCX ‘Legacy’, which runs full length.

The size of the magazine is approximately the same as for an MP5 and holds 100 BBs. On the sides of the magazine are raised dots which will certainly help with

grip in either wet or cold conditions. The magazine is also proprietary and although there are some rumours that MP5 magazines will fit, this is NOT the case. At the time of writing, the spare magazines are not yet available but I am assured (by those who actually know), that the magazines are made and sitting awaiting final finish before they are released for sale. I’d expect them to be freely available by around the end of January this year.

At the rear is a very nice sliding and side folding stock which has been at the top of a lot of airsofters wish lists for use on their MCX. It sports the same 1913 Picatinny rail which means it will accept any of the SIG MCX stock set ups giving a large range of options to the end user, from the sliding stock seen on the standard MCX all the way to the Helmet/Visor variant of the stock which is really useful for those who wear either lower face protection or full face masks. Also, as the rifle is a 1:1 replica of the real MPX you can fit a knuckle and GBB/RS buffer tube and fit any of the plethora of stock options that you can use on your AR/M4 builds.

The hand guard is a nicely shaped design with three full M-LOK slots on the 3 and 9 o’clock positions. Underneath there are two full and a third of a slot as the locking plate occupies the space where a full third slot would sit. There is still enough room to either fit a section of M-LOK Picatinny rail to allow fitment of vertical foregrips, finger stops, hand stops or barricade stops. Inside the hand guard there is surprisingly a lot of space for the battery, we’ve been able to fit a 1450mAH 11.1v battery pack, which should be enough for most players, but maybe not a full days play depending on your style of play. Even though this may be the case a battery change is easily possible in a few minutes so it won’t eat into your rest or reload time in the safe zone. When you take the hand guard off to access the connector for the battery, here is something quite new in out of the box rifles. VFC have used 2mm bullet connectors rather than the spade connectors of old. This makes taking the connectors apart and reassembling them soooo much easier. It may seem like a small, insignificant thing, but to someone who does a lot of custom builds and replaces spade connectors for bullet type this makes me smile.

The 168mm inner barrel comes in at 6.05mm bore. The hop is easily adjustable via the rotary disc. Early tests on the standard rubber gave good range, but as is the norm for a lot of rifles built in the East, the hop rubber can be a bit hard for a more temperate climate. For this rifle though the hop, after a small adjustment, was sending the BBs straight and true for a good 50m. I thought this was rather good for a short barrel.

MORE POP!

From the box, the sound on firing is really ‘poppy’. On this particular rifle I found that on both 7.4v and 11.1v the rifle felt like it was labouring. The main spring fitted to the MPX from the factory is an M120 delivering an average of 353 fps +/- 6, which goes some way to explaining why it seems that the underpowered 19TPI motor is struggling to turn the gears. For the UK this is still within the legal fps range but most sites prefer 328-340 fps. With the quick-change spring, I tried both an M100 and then an M95 spring to see what difference that would make. Immediately the motor sounded happier. The M100 gave 324fps and the M95 came in at an average of 312 fps. I would say that this is definitely the first thing to change to improve the performance. Returning to the motor and running a 1450mAH 7.4v LiPo, I still felt that this was lacking in the sort of performance that airsofters, in general, seem to want in an AEG. I first tried a 22 TPI motor that will deliver 25,000 rpm with an 11.1v battery. Even with the 7.4v, the 22 TPI made a lot of difference and I was a lot happier with the performance. In the interests of science and “I wonder what this will do”, I fitted a Warhead M brushless motor and immediately I went from “that’s OK” to “now that’s what I’m talking about!!!”

My opinion is that the first thing to change is the spring to an M100, this will take a lot of strain off the motor and make a substantial difference on the ROF. Next to kick it right up there, I would change the motor to something like the ASG 30k. Whilst not giving the performance of the Warhead, from a budget perspective it’s a better option. If ‘money is no object’ then definitely go for a Warhead Motor. This is all achievable without having to strip the rifle down and go into changing gears etc.

For all the external things on this rifle which are good or excellent, there is one part which I feel is not as good and that is the flash hider which is fitted on the rifle. It looks like a standard VFC birdcage unit and to make this an even better rifle I would have liked to see a SIG licensed flash hider or muzzle brake. Something like the short three prong flash hider or the QD muzzle brake would certainly knock this rifle’s looks over the edge and into truly stunning.

This rifle, as with the MCX variants, will be hugely ‘upgradeable’ internally and my colleague Dan has already had one in for some improvements over the standard build. I’ll let Dan explain what he has found and how he’s improving the internals.

DAN’S TECH TAKE

Moving on from the external side, let’s take a peek under the hood of the MPX and see what’s inside. Disassembly of the MPX follows along in the same vein as most any front-wired AR/M4 AEG with ambidextrous selector switches, so the process will be familiar to anyone wanting to crack open the gearbox; similarly, the MPX tears down almost 99% in the same fashion as its larger brethren, the MCX, does. Pressing out the captured front push-pin on the lower receiver allows one to slide off the rail and upper receiver.

After removing the hand guard, you can separate the wiring harness via a pair of quick-disconnects. At this point the upper can be removed from the gun. Once the upper has been slid off, you can access the hop up chamber and inner barrel. The hop up chamber itself is the same Ver. 2 rotary design as found in VFC’s current generational line-up, with the sole difference being the MPX’s version sports a larger diameter knurled ring to allow easier adjustment through the smaller ejection port window. The inner barrel is a standard AEG cut brass bore measuring 171.45mm (6.75”) long and is nicely finished out.

Regarding disassembly of the lower receiver, the minor point of difference between this and the MCX is the magazine button is retained by a hex head screw and the bolt release lever is also secured in place with a pair of small hex head set screws. On these latter two, care must be taken on removal as I’ve found they can be torqued in quite tight from the factory. In my example, I actually stripped the head on one of the screws and had to use a little elbow grease to remove it fully, where it will later be replaced.

The bolt release lever itself is a different design than the MCX’s and should be considered proprietary

to this gun. It’s designed for ambidextrous use, and here also the corresponding bolt release latch that is affixed to the side of the gearbox is also uniquely designed for ambidextrous operation. Aside from that, the rest of the gearbox is remarkably the same as the gearbox found in the MCX. After that, getting to the gearbox is just a matter of removing the quick-change spring guide, the motor grip, unscrewing the selector switches and drifting out a pair of pins.

The gearbox shell itself offers the same quickchange spring guide design as the MCX, so once you have the spring guide out, you can more easily release tension on the anti-reversal latch through the slotted window on the left side shell half. The outside of the gearbox also features the Avalon series ambidextrous selector gears and the standard metal Ver. 2 selector plate. Experience has shown that with some radiusing of the cylinder windows and the addition of Sorbo or AirPads, these shells will handle some heavy-duty springs without worry of cracking. On the inside of our gearbox, the air nozzle is VFC’s excellent Ver. 2 design and features an internal O-ring for better

“THE BOLT RELEASE LEVER ITSELF IS A DIFFERENT DESIGN THAN THE MCX’S AND SHOULD BE CONSIDERED PROPRIETARY TO THIS GUN. IT’S DESIGNED FOR AMBIDEXTROUS USE, AND HERE ALSO THE CORRESPONDING BOLT RELEASE LATCH THAT IS AFFIXED TO THE SIDE OF THE GEARBOX IS ALSO UNIQUELY DESIGNED FOR AMBIDEXTROUS OPERATION. ”

compression. The tappet plate is the current red version, and it appears that VFC have still managed to keep the plastic of these from being too brittle, as they once were infamously known for.

Even amongst such a most recent release, VFC are still regrettably using their existing cylinder head design; this example already has the typical hairline crack stemming from the nozzle shaft. Under continuous operation, this will eventually crack further and cause increased compression loss and potentially failure of the nozzle insert itself. Separation of the nozzle shaft from the cylinder head body is a common failure point seen on older-model, highmileage VFCs. A ported aluminium piston head rides on the front of the piston assembly. This is affixed via thread locker and has a small plastic insert in lieu of ball bearings found on some designs. The piston itself has a polymer body construction, with seven teeth (including the release tooth) on the front end being made of metal.

The gears are a standard 18:1 nominal ratio setup and, like current VFCs (excepting the SCAR series,

which is in desperate need of an update!), has omitted the self-shimming springs in lieu of steel shaft sleeves and shims. A plastic delayer chip rides on the sector gear. This particular example was shimmed on the tight side, and it was easy to see why: they only appeared to use one size of shim at time of assembly. On the subject of gears, I was disappointed to note that a gun with a premium price tag like the MPX did not come outfitted with the higher end internal package as found on the Avalons and Samurai Edge. Where 13:1s and the 22 TPA Neodymiummotor would have really complimented this build, we are instead treated to 18:1s and the old school 19 TPA ferrite motor. Tight shimming aside, this gear and motor combination also explains the lacklustre responsiveness and low rate of fire with 11.1v LiPos; the MPX feels especially anaemic with 7.4vs.

Finishing out the gearbox, the trigger switch is a standard Ver. 2 mechanical assembly with a MOSFET soldered to the contacts. These are relatively svelte setups that aren’t needlessly large and clunky, nor possessing fragile micro-switches, like some competitor assemblies are. That being said, they don’t favour especially stressful builds or having a lot of amperage pushed through them.

Overall, this is a pretty standard – if uninspiring – gearbox. Owing that it is a relatively bog standard Ver. 2 assembly, the upgrade potential of this gearbox is very high, to the point where everything that exists inside could conceivably be replaced with after-market options if you had money aplenty to burn. Looking to the future, we will be following up in a later issue with our “Dream MPX Build” to stretch out the capabilities of this gun to its fullest potential.

WRAPPING UP

Thanks Dan. So, to round off, this rifle is really, really nice to handle, but was a bit disappointing on firing tests initially. On our test rifle, once the spring and motor were swapped out the MPX performance picked up and will perform well on the skirmish field. Aesthetically it’s gorgeous but to tip it into the awesome bracket, the flash hider would be the first thing I would change externally, as I did for the photos of the rifle with accessories fitted.

Internally I feel, for an AEG rifle in the higher end price bracket, that the motor and gearbox internals should be better. Externally a really great rifle, but a couple of basic internal component changes internally will help the performance greatly and turn it into an awesome skirmish rifle. As with any product that is made for a client, cost is king and in some cases, where an OEM may want to use certain higher-quality, higher-performance components, they may have to be changed for other parts to keep the costs within those specified by the client.

The next thing that a lot of airsofters are already excited for is the gas blowback variants of the MCX and MPX. Any news on these models is very scarce. I’m sure though that it could be in the pipeline and it’s just a matter of time before SIG AIR make us even more happy and release GBB MCX and MPX variants. Please, please, please SIG AIR....can we have the gas blowback variants! :)

At time of writing to get an MPX from the UK distributor, Highland Outdoors, the SRP is £726 inc. VAT. With Airsoft Action being a worldwide magazine and as the MPX has not yet been released in the UK, the rifles we used for this review and testing were privately imported with the help of “friends in the orient”! If you’re based in the Asia-Pacific (less Japan) area, the exclusive distributor for the SIG AIR MPX is Redwolf Airsoft although, sadly, for legal reasons they were unable to send us a test sample in this instance. AA