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V2 Gearbox King Arms M190

8825 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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They put a metal piston head in that thing (and with a metal cylinder head)? Are they insane? Thank god the cylinder head seems to have a nice buffer, otherwise I'd say that mechbox shell is screwed with the M190. The use of bearings instead of solid bushings with a spring that strong doesn't sit too well with me either. Time would tell if they hold up. The gearset looks suspiciously like an Element tourque set, which makes sense considering they're known to OEM some King Arms parts. This is not necessarily a bad thing, as they are known to produce pretty good gears, but you never know how long they would last on the M190. And plastic spring guide for that spring? Really?

On the plus side (for you at least), I highly doubt if this would have any issues on an M130, provided the parts are all put together right (fix the AoE).

I don't know if you've handled sorbothane before, but if you have, does the buffer on the cylinder head feel like it? Because that's what seems to be keeping the mechbox shell from cracking under the power of the M190.

To answer your first question, I think it would be fine with the 420mm barrel, but I'd put in a full cylinder for a 509mm.

As for turning the bucking inside out, the easiest way I have found is to use a crochet hook to pull the nozzle end of the bucking through.
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