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Review

Top Tech M4 Carbine Blowback
  • Manufacturer 
     Top Tech
  • Model 
     M4 Carbine
  • Capacity 
     450 rds
  • Weight 
     3100 g
  • Power 
     328 fps
  • Motor 
     High Torque type
  • Hop-up 
     Adjustable
  • Battery 
     9.6V 1700mAh
  • Shooting Mode 
     Semi, Full Auto
  • Construction 
     Magnesium alloy, Aluminum, Polymer

Pros

-Reliable blowback system
-High performance and quality
-Unique design points
 

Cons

-Markings leave room for improvement
 

Verdict

Overall a very well designed and made AEG from Top Tech, with very good finishing, performance and multiple innovative and unique design points. Pretty much the only thing to wish for would be more realistic markings, or rather a blank receiver instead.

 

As soon as the first electric airsoft guns were introduced in the early 90's, many users have longed for something more realistic than the recoil-less action and sound of a sewing machine. Various blowback systems have been developed, with Tokyo Marui pioneering the idea with their PSG-1. That and the following blowback systems or AEGs have been mechanically linked to the piston to provide the blowback, but the return spring reduces Rate Of Fire, and the mechanical parts have not been quite as well designed as the original gearbox, so failures have been common. Also as the bolt carrier would move with the piston, the guns would commonly rack the moving parts before shooting the BB.

Using patented technology from G&G, Top Tech has released an AEG with a new kind of a blowback system. In this version, part of the compressed air is driven into another piston on top of the gearbox, and blowback action is provided simultaneously with shooting the BB for increased realism. Because there is no mechanical link between the piston and blowback system, jamming the bolt carrier won't affect the cycling of the gearbox. In fact you can hold the bolt carrier still with your finger, and the AEG cycles just fine!

This diagram shows the principle how the blowback system works. Lack of mechanical connection adds reliability of the primary mechanism in case the add-on feature should run into problems.
The outer barrel is one-piece CNC-machined aluminum all the way, and secured to the upper receiver with a proper barrel nut.
The markings on the left side leave no doubts of the country of manufacture. An all-black version would be our favorite.

The AEG is shipped in a similar fashion as G&G AEGs in a sturdy styrofoam packing inside a colorful cardboard box with manufacturer information printed on it. As soon as you lift the Top Tech M4 from the box, you notice that it is made in a very solid fashion with no flexing or creaking to be found. It has a nice heft of 3kg to it, which is very close to the weight of the real thing.

The plastic parts are all nicely made from polymer, and seem as strong as they look. Obviously the handguard has no heat shields to make room for the battery (9.6V 1700mAh twin pack type), but other than that they look just like their real counterparts. The finishing of all metal parts is nicely made, and nothing stands out negatively in the workmanship. The designs of the markings are not exactly to our taste, but we have to admit they are nicely etched as well. Because of the special spring release system, other AEG etal bodies are not directly compatible with these models.

The right side markings are quite plain. Note the lack of screw on the mag release: The construction is realistic and durable!
The pins have retainers to keep them from falling out, and the wires can be disconnected for easy disassembly.
The blowback system is packed into a really small space above the gearbox.

The recommended battery for the Top Tech M4 Carbine is a 9.6V 1700mAh one, so we plugged one up and closed the handguard. As opposed to many others, the delta ring only required a reasonable amount of force to pull back, but in the closed state the handguards are plenty solid and won't fall off. The specified battery gave a nice RoF and quite a short delay for the first shot. We went through the first full 450 round hi-cap magazine in just two minutes simply because it was just so fun to shoot!

As we have come to appreciate with G&G AEGs, the Top Tech offering provides stable muzzle velocities. Because some lubricant gets from the gearbox into the barrel during the first few hundred rounds, you should pay attention to cleaning the barrel especially in the beginning when you start using a new AEG. Once the barrel was cleaned, the Top Tech M4 provided very consistent muzzle velocities at 328 fps / 1 Joule, which is perfect for CQB and countries where the legal energy limit is low.

The grip end is heatsink-type with a fairly sized motor height adjustment screw.
Underneath you'll find metal threads embedded into the polymer grip for improved durability.
The hop-up chamber is plastic, but does the job quite well. A brass spacer ring holds the barrel centered.

As pioneered by ICS, the Top Tech M4 Carbine features a working forward assist. Well, sort of. As opposed to the real thing that forces the bolt carrier forward, the forward assist on an AEG is described as a working one when it releases the spring tension. Inside, it is linked to the anti-reverse latch to allow the gears to turn backwards and release the compression for storage.

The blowback system isn't really hard-kicking, especially since we still remember the GBB M4 from WA so well. If you shoot without BBs, the bolt carrier barely moves, because all the air escapes from the barrel. With BBs there is sufficient back pressure to propel the system. We chronoed the gun with the bolt carrier mechanically jammed, and the velocity difference was only 3-4 fps, so it is rather economical and doesn't really sacrifice performance. The bolt carrier can be locked open for hop-up adjustment.

The forward assist knob is linked to this transfer bar on the inside, which disconnects the anti-reverse latch to release spring tension.
The bolt carrier can be locked back just like on the real one. As usual, this makes hop-up adjustment easier.
The mock bolt carrier from stamped steel wraps around the top of the gearbox, instead of the typical simple construction.

Going into the insides was a bit concerning at first, since we didn't know what kind of delicate parts would fall out as soon as the receivers would be separated. The worry was unwarranted, since all the parts stay in their place quite well, and disassembly works almost exactly the same as with most other AEGs.

First the battery wires are disconnected, since this is a front-wired model. Small connectors are provided, so you don't need a soldering iron. After pushing out the captive front takedown pin, the upper receiver can be slid forward off the lower. You do need to release the charging handle lock at the same time, and the handle stays on the lower receiver instead of coming off with the upper.

An ingenious link connects the left and right side of the selector, so you can see the setting on the right side of the receiver.
The gears are die cast, but shimmed very well and run smoothly. The box is greased generously as well.
The piston is a durable fiber-reinforced one, with the second tooth removed as the trend is. The piston head is aluminum with 8 ports.

After the usual removal of the grip and stock, the rear takedown pin and "trigger pin" are removed. Note that the trigger pin should be knocked out in the opposite direction compared to the takedown pins. The magazine catch construction is similar to the real thing: It has to be pushed in deep enough that you can rotate the large L-shaped part on the other side of the receiver until it comes off. This eliminates the ugly and easily-loosening small screw that almost everyone else still uses. Thumbs up for this small touch of realism and durability! Lifting the gearbox out from the lower lets the left side selector indicator fall out, but it is easy to align later when assembling.

The gearbox features 8mm bearings and a superb shim-job for smooth and durable operation. The gears themselves are die-cast, but are quite strong material. The spring guide has a bearing on it for smooth compression cycle, the piston is fiber-reinforced polymer and all pneumatic parts are well sealed. Thanks to the O-ring even inside the nozzle, the entire system is airtight for best efficiency.

The front of the box has a slight radius to reduce the risk of cracking.
The cylinder head has the best damping we have ever seen! Thick enough to soak the impact, it also has a funnel shape for good air flow.
The air comes out from the top of the gearbox (middle) into the brass blowback cylinder (bottom), and propels the piston (top).

The aluminum piston head and the front of the gearbox seemed like a combination for trouble first, but the radiusing of the gearbox and rather impressive damping of the cylinder head convinced us in that regard. It is unlikely that the user would run into any kind of problems with this system.

There's no question that this is a very well made AEG from Top Tech, and the performance and reliability have not been sacrificed to produce the blowback system. With this many design points in one package, it is a worthy weapon to consider even if you are not that interested in the blowback feature!

The rear of the upper receiver has rather large lugs that go under the lower receiver for a solid connection.
An adjustment tool to zero the front sight for elevation. Still remember our article how to zero the sights?
A wrench is provided to remove the flash hider and loosen the barrel nut if necessary.