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V2 Gearbox King Arms M190

8824 Views 2 Replies 2 Participants Last post by  recoil
King Arms
"Ver.II Front Wiring Complete Gearbox for M4 Series - M190"

I recently bought this complete gearbox from ehobby, and I thought I'd review it, since it is an excelent base for an M4 DMR. It cost me 133$ without shipping, and here is the link.

Allow me to start by assuring everyone that I do not intend to use the M190 spring it came with, but all other variants (m135, m150) were out of stock at the time I made the purchase, and I wasn't sure that the parts in the M120 version were the same as the other versions, so I bought the gearbox with the highest chance to cycle an M130 spring without problems.

So here I go:

At first glance, you can see the 9mm bearings, silvered wires, and the cylinder perforated for 300-400mm inner barrels (so they say), the reinforcement of the gearbox.

King Arms vs. Dboys

Inside the gearbox, lots and lots of grease of course.

The M190 spring that came with the GB (bottom), along side a Systema IPTS M130 which I forgot compressed in another gearbox for about 2 months. Not sure if you can tell from the picture, but the M190, although shorter, it is a bit thicker.

Polycarbonate piston with 7 metal teeth, aluminum ported piston head with it's o-ring. The cylinder head fits so tightly inside the cylinder, I didn't feel the need to wrap it in teflon tape.

The tappet plate is listed as "durable", don't know what else to tell you about it. The air nozzle is plastic and has an o-ring inside.

The spring guide, obviously isn't metal, but it does have bearings. Here it is next to the stock cylinder.

The gears are steel, high torque, 100:200 ratio, and to my surprise, helical (even though the specs say only reinforced). The shimming, to my surprise, was close to perfection.

Unfortunatley, I didn't have access to a chrono at the time I opened it, so I have no ideea what the M190 might have shot, but I could tell from the slight pain I felt in my ear after a few shots on semi that it was louder than anything I shot before.

I will be using this gearbox with an M130 spring in my Dboys SPR, for my 'silent dmr' project (which is almost done), and I have a few questions:
1.Do I have to change to a full cylinder to use it with a 420mm or maybe a 509mm inner barrel (both 6.03)?
2.How do I turn a hop-up rubber inside-out without tearing it?

EDIT: Chrono'd the M190 spring, it clocks at 164m/s (538fps)
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The rubber buffer on the cylinder head is pretty rigid. I don't know how it feels compared to sorbothane, all I can say is that it was very loud. I will be getting my hands on some sorbothane soon, until then, I'm experimenting with 3 layers of mouse pad mat.

Also, I know that the spring guide, bearings and piston head are completely bonkers for an M190, but I'm pretty sure they use the exact same internals in their lower power spring versions, which I guess make more sense.

Oh, and thanks for the tips!
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