Double Eagle M66 / M700 PRO unboxing

While the gun is built mostly using alloys and nylon as its main construction material, steel is used instead for the collapsing stock's hinge sections. This hinge can be disassembled and flipped sideways to convert the stock's folding direction without extra parts.


Primed indicator (painted in red) located at the back of the bolt assembly.


An ambidextrous safety lever. Unlike other rifles such as the VSR and M40 which often has a protrusion sticking out from the receiver awkwardly, the M66's safety lever is more well concealed, reducing the likelihood of accidental engagement when the bolt is pushed back into the receiver.

The hop adjustment knob located under the stock. The M66's adjustment knob is smaller in diameter compared to the Marui M40A5's knob.
An interesting detail unique to the M66 is rather than blindly copying from its Marui counterpart, this knob has a positive click feedback system instead of a smooth fully rotating knob with no resistance in between, which is a commendable improvement in itself.

The two hex keys that came with the rifle can be stored within the grip and tightly held together by the bottom cover. These keys are essential in disassembling the entire rifle.

The grip position, cheek rest height and buttstock position are all fully adjustable. Unlike the Pro 700 however the buttstock is a one-piece rubber pad and can only have its length adjusted - the height/angle adjustment functionality is omitted in this replica.

The stock can be unlocked by pushing a rather sizable button on top of the hinge joint. The then-folded stock is engaged by a spring loaded bearing which prevents the stock from unfolding itself spontaneously, but it's otherwise not locked and can be un-folded easily. The handle is fully hidden within the folded buttstock.



The gun comes with a total of 5 QD sling points. The handguard and buttstock both have a pair of them installed on both sides of the rifle, while the last one is installed right next to the bolt handle. (This part is also ambidextrous and can be swapped to the other side of the rifle if required.


The rifle clocks at 1.08m in length, weighting at 3.7kg (about 300 grams heavier than the Marui M40A5).

M66 bolt in action
Similar to the Marui M40A5 the bolt handle is exceptionally smooth, with a shorter bolt pull than the VSR.


OOTB joule count using 0.2g BBs is at ~1.75J and at ~1.85J when 0.28g BBs are used, a rather high value for a stock rifle.
(note from translator: it was later tested that this gun still creeps positively even when 0.4g+ BBs are used by really big margins, which considering the short pull and low air volume, is pretty incredible in itself.)

OOTB M/S variation using 0.28g BBs is at 2.2m/s maximum, a passable if unremarkable variation.

Rifle Disassembly


Magazine disassembly. The entire magazine's internals can be detached by undoing the two screws beneath the magazine that is usually hidden by the mag plate.

The magazine design is different from the M40A5 as well - while the M40A5's magazine only has one latching point behind the magazine engaged by the mag release button, the M66's magazine latching point also pushes an another lever inside the magazine, which will thrust an another latch inside the magazine into the rifle itslf.
Compared to the Marui system, the M66 magazine system ensures a more consistent engagement with the rifle's feeding tube lever even with loose tolerances between the mag well and the magazine, allowing less resistance and a more snappy "slot in" action somewhat similar to M4 AEGs.
This also means the M66 magazine is proprietary and cannot use Marui M40 mags.


The magazine has a 52BB capacity; however 10 BBs are required to fill up the feeding tube beforehand.

Forward rail weighting at 86gs allows the installation of additional accessories such as IR or cameras, and can be detached with no ill effects if desired.

Unlike the APS Barrett Fieldcraft, the M66 does have the "funnel" shaped barrel typical on M700 rifles modelled correctly rather than reusing the oversized VSR barrel design, which is again a commendable detail considering the price point of the rifle.


3 screws located at the trigger guard, within the mag well, and inside the handguard well hidden within the M-LOK slot can be unscrewed to detach the whole stock from the receiver. These screws are held in position and will not fall off from the stock even if they are undone.

The Magpul Pro 700 stock. Due to having different attachment points the Pro 700 stock is unique to the M66 itself and cannot be swapped with other existing rifles.

Comparison between the M66 and the Marui M40A5. Although largely inspired by the M40 system, the actual design is quite different to the point it's safe to assume they are incompatible with each other completely.

The spring guide stopper can be detached after the screw used to hold it in place is undone.

The bolt assembly is aesthetically pleasing, with a spiral fluted cylinder body with a straight-cut bolt.

Comparing the M66 bolt assembly with the Marui M40A5 bolt assembly. The M66 bolt is visibly longer than the M40A5's.
It can be assumed that due to a larger cylinder volume as a consequence of a longer bolt, the M66 should be able to support heavier BBs or longer inner barrels.

The piston is a 45 degree system design. For some reason the alloy spring guide actually comes with ball bearings stock, also a design feature unheard of in stock airsoft guns.
(Note: The original author might actually meant "a design feature unheard of in stock guns at such a low price rating")
The bolt assembly is completely incompatible with the Marui M40A5's bolt assembly internally, sporting internals of different lengths and dimensions.

The spring's outer diameter is roughly similar to that of PDI's. (ie. 9mm/13mm)

Primed indicator disassembly. The entire assembly can be undone using a flathead screwdriver.

The primed indicator assembly of the M66 is remarkably different and much simpler compared to the Marui M40's approach. Instead of a complex design involving the trigger assembly, the M66's approach only requires the piston which pushes the indicator backwards as you cock the rifle. This system could probably be copied and used on VSR upgrades due to its relative simplicity?


The bolt handle can be detached from the bolt afterwards. This bolt handle is the only "not ambidextrous" part of the rifle and requires an additional "lefty" bolt to complete its lefty transformation.
Similar to VSR bolts there are two spring and bearings to hold the bolt handle in place.



The trigger assembly. Two silver bearings can be found in the trigger assembly to assist sear movements, yet an another unusual feature for an OOTB rifle.

The trigger's engagement distance is adjustable using a hex key (which is also the only thing that can be adjusted in this trigger assembly). That a lighter trigger spring is recommended due to its rather hefty trigger pressure.


Barrel disassembly. A simple, if labor intensive process due to the large amount of parts involved.
The hop up knob is held onto the rifle using 3 screws, which can be undone and detached from the rifle.

The feeding tube can then be accessed and detached from the rifle by undoing the 4 screws holding it in place. This is a system commonly found on airsoft rifles that has a realistic magazine placement in order to connect the hop up chamber with the actual magazine residing behind it.

Feeding tube system showcase. As long as the magazine has BBs inside it, the lever above will be pushed upwards by the mag's lever and open up both exits on both ends of the feeding tube, allowing the gun to be properly feed with BBs.

If the magazine is detached or no longer contains any BBs, this lever will no longer be pushed by the magazine's own lever system (which now will cease to be engaged by BBs inside it) and both ends of the feeding tube will be shut off, preventing any BBs from being fed into the gun.

The hop up chamber block can be found after detaching the "see-saw" mechanism beneath it which was held together by two screws and a pin. This seesaw is the integral part of allowing the hop up arm to be "pulled" by the hop up knob.

By detaching the hop up chamber block, the actual hop up chamber then can be seen from the opening.

Unscrewing the outer barrel from the receiver. The diameter of the outer barrel is identical to that of the Marui M40A5 (both thinner than the VSR outer barrel).

The hopup assembly can then be detached from the outer barrel entirely. Note that due to having an O-ring stabilized barrel spacer inside, there is a notable amount of resistance when doing so, it's easier doing so by pushing the inner barrel inwards instead.

The BB stopper assembly. Like most competent designs a plastic assembly here reduces abrasion and damage done to BBs which improves performance as a whole.

What the hopup assembly should look like when fully assembled. Note that there is a hopup nub separate from the assembly which provides pressure to the hopup bucking directly.

The "fang"-like protusion of the bucking.


Hopup chamber disassembly. This chamber is made up of a solid block of metal, and unlike the Marui M40A5 it uses standard VSR buckings and barrels and doesn't have any extra cutouts nor protrusions for stabilization purposes.
While the bucking itself doesn't have the bar protrusion found on regular VSR/GBB buckings (similar to the Maple Leaf Super/Wonder buckings), a cutout for regular VSR/GBB bucking's bar protrusion is still there and the chamber itself supports regular VSR buckings without any issues. (Owner of this rifle replaced the bucking with a PDI W-hold instead.)


The inner barrel is a regular VSR spec barrel at an unusual 410mm length.

The barrel stabilizer is held using friction only and can be put onto other inner barrels without issues.

For a rifle costing a mere 1700HKD (~220USD), it is mind boggling for Double Eagle, who is more well known for making very budgeted airsoft guns as a whole, to create the M66 while having internal and external quality rivalling rifles that would normally cost 3000HKD (~400USD) or more.
With an internal system improved upon the well crafted Marui M40A5 system, and a currently one-of-a-kind externals that is also very well made despite its price point, it is certainly a welcomed choice for all involved as long as the Pro 700's design is to one's liking.

TLDR for those that are more interested in the technical/compatibility parts of this gun:

- This gun is a mostly proprietary system that is highly inspired by the Marui M40A5 system with some improvements, ie positive feedback clicking hop up adjustment knob, larger cylinder, simplified priming indicator, much better capability in hopping heavy BBs, better chamber compatibility.

- This gun's cylinder internals are off spec, both slightly wider and longer than the Marui M40, thereby is completely incompatible with any aftermarket parts made for the Marui M40A5.

- The hopup assembly accepts aftermarket VSR parts. Inner barrel length is 410mm, any longer and you will need a flash hider or silencer to shield the protruding inner barrel.

- The trigger assembly is of different spec from the Mauri counterpart.

- The magazine is also proprietary to itself.

Dang, that's actually super sweet. I heard Double Eagle and almost dismissed it as a whole, but that's actually a pretty well done rifle. Are there any compatible 90 degree trigger/piston sets available?

Nevermind, looks like the trigger wax already addressed.

Yeah I think the only real upgrade that needs to be done is probably a steel cylinder and a steel sear set (or maybe a piston for good measure). This rifle itself is structurally sound and pretty well designed with so many notable improvements (instead of "fuck you proprietary") that actually makes a difference.

TenshouYoku said:

(note from translator: think Striker series or the SRS where you can tilt the gun and feed a BB into it - not happening with the Marui M40 system)

Click to expand...

Don't besmirch Strikers, Strikers are not ramp-fed rifles actually as a matter of fact I don't think SRS rifles are either? I know that the ASG M40A3 Proline and Ares MSR 338/700 rifles are ramp fed, along with a few others. Nonetheless, not your fault 😅 lost in translation.

That is a very neat feature with the lever locking feed tube though. I remember your other post, the Silverback TAC 41 had one of those features as well. I'm glad they're starting to be incorporated into more rifles, however I know that this will lead to compatibility issues down the line.

is the DE m66 spring compatible with the TM M40A5 spring? Trying to look for upgrade spring m160 equivalent or higher, can't find any ATM.