Arcturus GR16 MOD5 - great resemblance, good performance

Arcturus GR16 MOD5 - great resemblance, good performance
A new MOS/Arcturus replica. In less than a year from commencement of design work, a carbine modeled after the HK416A5 hits the market. Another step forward for the Chinese manufacturer?
In this article
PAGE 1: GR16A5
PAGE 2: Technical details


The new Arcturus GR16 MOD5 is a carbine modeled after the HK416A5. It is not a licensed replica, therefore it does not have markings compatible with the original, but the care and degree of recreation of the original are very high. In Europe, the replica appeared only a few days ago (mid-January 2020), it could be found slightly earlier in Japan. The Japanese version differs from the European one with 2 details. Firstly, it has a slightly lower muzzle velocity resulting from local regulations. Secondly, it has perfectly recreated HK markings, identical to the ones found in the real carbine. Well... Japan has slightly different regulations governing these issues. The reviewed replica comes from a batch intended for distribution in Europe hence, for obvious reasons, it is deprived of any markings that could even suggest its relationship with Heckler & Koch products.

What is the current position of the HK416 on the firearms market does not need any explanation to anyone who is interested in military technology. Exactly for the same reason, replicas of this weapon are enjoying constant, if not increasing, interest. And despite the lack of significant technical differences, an increasing number of players are exchanging their old regular AR replicas for the iconic HKs.

The reviewed replica opens a new Arcturus product line, which, as we have learned, will ultimately consist of at least several different products. We don't know when the next ones will appear and how they will differ. The MOS company, the owner of the Arcturus brand, decided that the A5 with a 9-inch handguard and a 10.5-inch barrel in 2 colors: black and tan, will appear first. We had the opportunity to shoot from both, but we got the black version for testing. But before writing about the tested carbine, first a few comments about the tan version. Although we do not want to discuss here the color nuances, we do distinguish, for example (is it a shame to admit ?!) the emerald color from plain green.

Note no. 1 — polymer elements, i.e. the grip and stock look reliable and good.
Note no. 2 — the receiver is covered with a homogeneous matt coating that is neither metallic nor glitter like.
Note no. 3 — aluminum parts, i.e. the handguard and the buffer tube, are powder coated. In our opinion, the color obtained is a bit too golden and shiny.

We have no comments about the color of the black version.

Basic technical parameters:
- overall length (collapsed/extended stock): 730/825 mm;
- weight (with an empty magazine, without a battery): 2850 g;
- inner barrel length: 280 mm;
- inner barrel diameter: 6.01 mm.

Of course, the carbine has the ability to quickly replace the spring from the outside, without removing the gearbox.

The replica is supplied with a mid-cap type magazine with variable capacity. The standard capacity is 130 BBs. After moving a plastic pin, the capacity drops to 30 BBs. This is exactly the same solution that Arcturus also uses in magazines supplied with other of its replicas.

The muzzle velocity declared by Taiwangun is 400 fps. The tested replica shots slightly better, but more on that later.

Visually, the replica looks great. It is impossible to have any remarks on the accuracy and precision of manufacturing of individual components. Also, the assembly and fitting are at a very high level. The connection between the upper and lower receiver is rigid and there is not even a slightest gap. The handguard's fitting is similarly rigid and precise. Even the stock is assembled much more precisely and tightly than in most replicas known to us.

Particular attention should be paid to exceptional attention to reproduction of details. The replica is simply a faithful copy of the original firearm and not a fairly casual "variation on the theme", with a catchy name slapped on to it.

Lets look at them closely. Double-sided, fully functional manipulators are placed in the right places and look as they should. The safety/selector switch works with a clear "click" sound, but when using the right lever, it is clearly less noticeable. The enlarged and characteristically curved trigger guard allows to operate the trigger in really thick gloves.

The pistol grip with a slightly changed angle is no longer new thing on the airsoft market, but it is worth noting that it fits well with the lower receiver.

The screw securing the handguard, differently than in the previous versions, is designed to be unscrewed with a wrench or some kind of flat tool.

The gas regulator clearly "clicks" when set in the right positions (and does not spin freely).

The stock is a copy of the HK narrowed stock of a new design. He fits very tightly. There is no lateral play on the guide. The crown nut is enlarged, as in the original.

The sights are made of metal and can be folded. The non-adjustable front sight in the folded position hides in the frame of the handguard and does not hinder the use of optical or optoelectronic devices. The folding rear sight is horizontally adjustable with a large screw on the right. Height adjustment is achieved by pulling it's upper part and rotating it around the vertical axis (in half-turn increments).

Removing the sight is done by sliding the mounting slider back. Everything is done exactly as in the original carbine.


Connecting the battery

The space for the battery is provided in the buffer tube. Access to the compartment is obtained by pressing a small latch at the bottom of the stock and sliding the butt plate down.

The space is limited and it will be difficult to fit a package larger than an 11.1V 1200mAh LiPo battery, and a single module version will work best. We also tried to use a dual module one, but due to the additional connecting wires it was already very tight inside.

If you want to use an 11.1V battery, there will be no safe or convenient way to install a mosfet, which the replica does not come with. There is a way around it, of course, by storing the battery somewhere on the outside.

HopUp adjustment

We open the polymer ejection port cover by pulling the charging handle back. The dummy bolt carrier "clicks" when it comes to the extreme rear position, making adjustment easier. The replica uses a rotary type chamber, which is slowly becoming the standard. Adjusting the HopUp using a large knob perpendicular to the barrel's axis is more convenient and precise. After completing the adjustment, you can release the dummy bolt carrier using the right or left bolt catch button - both are functional. We noticed that the dummy returns to its default position smoothly and dynamically.

Spring change

At the beginning, we noted that the replica's design allows the spring to be replaced without having to remove the gearbox from the receiver. This is possible after removing the buffer tube. How to we do it? Well, for starters, it is worth disconnecting and removing the battery. As a rule, it is not necessary, but the limited amount of space inside the tube prevents the battery from moving freely while unscrewing the guide, and this in turn can lead to twisted wires which can result in them or the battery get damaged. The next step is loosening and unscrewing the crown nut. It's best to do this with a dedicated wrench but, of course, you can also use slightly more invasive methods.

Next, we unscrew the guide from the receiver and after unscrewing the stabilizing screw, gain access to the spring guide, which is easily removed with a flat screwdriver.

By the way, it is worth noting the unusual solution that protects the end plate of the lower receiver against rotation. It is a special plug which fragment enters the hole in the plate and stabilizes its position.

And one more remark or warning. When screwing the guide into the receiver, you cannot do it all the way through, because you risk cutting the wires. When you encounter resistance, move it back to the last correctly oriented position and lock it with the crown nut. Let the properly tightened crown nut be responsible for stable fastening of the buffer tube.

In addition to the obvious risk of damage to the wires, the depth of screwing in the buffer tube affects one more thing. If for some reason you have dissembled the carbine by separating the upper and lower receiver and unscrewed the buffer tube, then reassembly is worth carrying out in the following order:

1. connect the upper and lower receiver;
2. screw the buffer tube with the assembled receiver.

The point is that it is possible to screw in the buffer tube deep enough that it will not be possible to completely slide the upper receiver on. If lower with upper receiver will not connect properly, it is impossible to insert the front pin. If you have already done so, unscrew the buffer tube by 1-2 turns.

Magazine capacity change

Arcturus supplied its replicas with interestingly designed magazines, whose capacity can be changed "on the fly", without using any tools. The one that comes with the GR16 also has this feature. The standard capacity at which the magazine works, and flawlessly we might add, is 130 BBs.

You can easily and quickly reduce it to 30 BBs. How do you do it?
First, press the rectangular part in the center of the magazine's floor plate and, holding it, slide the entire foot off. Then, partially slide the magazine's inner insert out of the outer translucent housing and slide a switch. In the photo below, the red arrow indicates the floor plate's latch, the yellow one point to the switch used for changing the capacity.

The gearbox

From the technical side, the GR16 is noting surprising. It is made in a standard known from other Arcturus replicas. The gearbox is a characteristic, slightly modified V2. However, this is a new generation of the frame, which differs from the previous ones in the areas of the anti reversal latch and the possibility of releasing it with a special lever. The shape of the frame is worth paying attention to - a modification of the rear part does not allow to be replaced it with a typical V2 frame. In the photo below, the gears visible are responsible for transferring movement of the safety/selector switch from the right and also the you can seen the right bolt catch, which must be removed to open the gearbox.

On the left, you can see a custom selector plate and the trigger safety working with it. Next to it lies the lever for releasing the anti-reversal latch.

Here the lever is mounted on the anti-reversal axle. A deep wire channel is also visible here.

The vast majority of the parts of the mechanism comply with the unwritten standard. Only the trigger cooperating with the micro switch is different, but this solution is already known from earlier Arcturus replicas. Also the anti-reversal, mentioned above, is different.

Other parts are standard:  the gears made of sintered steel with a delayer on the sector gear, am airtight cylinder assembly with a steel toothed piston, a spring guide and piston head with bearing, a nozzle with an O-ring. The gears rotate on 9 mm mix of bearings and bushings. The sector and spur gears use bushings, which ensures greater reliability of operation. Only the fastest rotating bevel gear is mounted on ball bearings.

Target shooting test and muzzle velocity test

When shooting, the replica surprised us with how it sounded. For some reason the recorded video does not reflect it, but the sound of the working mechanism is quite pleasant, but of course, it's a very subjective feeling. When it comes to ergonomics, the replica reproduces the original carbine very accurately, which is praised by those who have something to say in this matter have. All in all the replica is great. We will only add that it is impossible not to notice and underestimate the difference in placing a new narrowed stock in the shoulder pocket.

Target shooting tests have shown that the replica shoots correctly by all means, but it does not surprise with anything special. The"rotary" HopUp chamber gives a bit more control over the system than traditional chambers. Despite the use of a 6.01 mm inner barrel, we will not make a DMR out of the  GR16. The 280 mm long barrel is not very suitable for this. It should be noted, however, that the reviewed replica was perfectly aligned and the barrel was always in one axis with the cylinder and the nozzle. The results of muzzle velocity measurements and target shooting tests are presented below.

Muzzle velocity measurements

OpenBlaster 0.2 g BBs, ambient temperature of about 20°C, HopUp set to zero.

Muzzle velocity:

1. 409.5
2. 409.8
3. 408.0
4. 412.0
5. 409.8
6. 410.5
7. 411.1
8. 411.2
9. 410.4
10. 410.8

Average: 410.3 fps. It is 10 fps higher than the one declared by the manufacturer.

Spread: 4.0 fps - superb.

Target shooting test

Hop-Up was adjusted, G&G 0.25 g BBs were used, distance to the target was 25m.

Single fire



The new Arcturus certainly does not surprise with its configuration, performance or tuning potential. It is an excellent proof that some Chinese manufacturers pay more and more attention to the quality and care in designing and making replicas. The regular store price set by Taiwangun is about 280 EUR. This will, in our opinion, result in sales problems of the licensed VFC/Umarex carbine in the near future, which, until recently, had no competition. Of course, Arcturus will not convince everyone, because the lack of markings and the not exactly correct color of the tan version will remain an unacceptable compromise for many. However, we expect that the significantly lower price will compensate these inconveniences for many people.

More photos can be found in the attached galleries.

The replica has been supplied for testing by its imported -

On the next page - technical detail for those of You interested

In this article
PAGE 1: GR16A5
PAGE 2: Technical details

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