AOSC Forum Archive

Good evening ladies and gentlemen.  I have a taboo to bring to light, something that is generally pushed to the side with the thought "It won't happen to me", however it did happen to me, and I'd like to share.

Here's the link to the video.
KWA M16 2GX Gearbox failure.
Pardon the portrait view, working on a fix.


Some user history
Bought on the 29th of December, 2010.  Less than 4 months ago.  Have shot Matrix, TSD, and finally stopped at KSC.  Using assorted .25 and .28 weighted.  Have shot less than 20k rounds through this gun,  I have not abused this rifle by firing full auto non stop, and I have only run a 9.6v 3800 mAH Tenergy battery through it.  I have cleaned and lubed the barrel after every game.

Looks like the piston is broken/stripped. You're hearing the gears spinning with no resistance, and there's just enough left on the piston to baaaaarely pull the air nozzle back.

Thanks for confirming my suspicion.  If I am not mistaken, the piston is proprietary, therefore it looks like a $35 fix.  http://store.kwausa.com/partsaegkm4seriesejectionportcoverlock-1-6-1.aspx

Anyone else experience failures with KWA?

If they're proprietary its news to me.

I don't have any experience with the 2GX KWA's but me and teammate both experienced a good bit of failures with the 1st gen KWA's. The problems ranged from broke pistons(not stripped, BROKE), vaporised sector and pinion gears, broken trigger components, complete outer barrel falling off the gun, constant magazine compatibility problems due to KWA copying Mauri and making a mistake in the magwell on some of the earlier models. All of these failures happened by using a regular battery, not a LiPo like KWA said they were ready for. 1st gen KWA's pistons were thicker than a normal piston as I found out the hard way so the 2GX piston may also be the same.

By "lubed the barrel", you don't mean you left lube in it after cleaning, right? See #7 here: http://www.southcarolinaairsoft.com/forums/http://www.southcarolinaairsoft.com/newforums/viewtopic.php?t=1

SteevoLS wrote: Looks like the piston is broken/stripped. You're hearing the gears spinning with no resistance, and there's just enough left on the piston to baaaaarely pull the air nozzle back.

Actually, the piston has nothing to do with the air nozzle, that is cycled by way of the tappet plate which is cycled by the sector gear.

The fact that the air nozzle is cycling means that it is not the gears, and thus is the piston. The lack of  a grinding noise (which would be indicative of some resistance) means that it was a clean break, the rear tooth of your piston has broken completely off.

This is a relatively common failure point in polycarb pistons, you will obviously need to replace the piston. KWA pistons are slightly unique (all pistons are), they are by no means strictly proprietary. You can put just about any piston you want in that gun.

Yes, Dom, I mean I followed your instructions xD

So, with that being said, I will be sure to get a piston with a stronger last tooth.  Time to pour some time into google...

I have had both 1st and 2nd gen kwa gearboxes, and I have had good experiences with them for the most part but did have some things happen over a period of time:

Heres what happened to 1 of my KWA's.
1st Gen M4, I put a m130 and shot about 460 FPS w/ .20's. Shooting semi-fire I ran about 120K rounds until my hop-up started to wear down. Replaced it then after about 250K rounds total my Gearbox shell cracked at the front where the piston is located. I also started to notice my hop-up was falling apart so, I replaced both with 2nd gen kwa parts. New 2g kwa hop-up, madbull nub, and the 2g kwa reinforced gearbox shell which was much thicker, especially around the front of the shell where mine so happened to crack. The gears, piston, and other internals had NO noticable wear, surprisingly. The gun was assembled for the end result of an extra +10 fps on the smoother, more silent gearbox and some extra distance from the new hop-up.
2nd Gen kwa's a certainly superior to the previous models. The gearboxes are good to me, but I have seen quite a few crapped out kwa hop-ups out of the box. Other than that they are a solid gun and well worth the money IMHO.

I have done my research, and time and time again I see the good stories.  I expect as such, and the guns long and steady life.  Despite the one of the greatest QC's around, KWA still has some of their holes.  I just happened to fall through, no worries though, just get a new piston and I'll be set.  And with my new aquistion, I'm questioning how much use this one will get.

http://www.youtube.com/watch?v=Ae4WCTMV ... ideo_title'
Update, do not mind the sexual puns....

How do you mean no shimming whatsoever? Seeing the back tooth missing, can I assume you were running it on a high ROF battery setup?

There was just no shims there, it was right up on the bearings themselves, right on the gearbox, every one of them was. And it was a 9.6v Tenergy battery, last time I checked that is not a high ROF Battery setup, but I could be wrong.

I see. Fail.

Agreed. Zach and myself will be ordering a new piston, and new shims to apply to the gearbox, which will make it sound alot better, as it sounded quite nasty inside....

Any retrogradations on a piston? We are looking for metal teeth with a poly carb body...

Wow, I know just the place, what a great coincidence! I heard of this new store called SC Airsoft Supply that has exactly what you want in stock right this minute! You should totally PM the owner and ask to do a Beta test right away!