Masada finally works (new gearbox)...

[GI Joe]

Well I finally got my Masada working and it is working beyond my expectations.  All it took was a new gearbox.

I ended up buying a JG Enhanced Gearbox (rated for M130 Springs) since it was more affordable for my current budget than the G&P (came to about $55 Shipped).  The only modification required to the gearbox was adding a Masada length nozzle (I ended up using my double o-ring Masada nozzle).  I kept everything else in the JG box exactly as I had gotten it.

The action of the gun sounds smoother than it ever has, and the motor no longer sounds like it is working too hard.  Even when firing on semi-auto as rapidly as possible I have not been able to get the gearbox to lock up (not even partially cycle).  Went through about a mag and a half for some testing at the BCM training day today and had no problems.  I still haven't been able to chrono it yet, but I think we can close the case on this one as I lay the A&K gearbox to rest.

Thanks to everyone who helped me, I really learned a lot and finally got the Masada working how I wanted it to. 

[Bishop]

I can't say how happy I am that your Masada is working as you expected. I felt the same elation once my GBBR issues where addressed and I could finally use my gun in a game.

Get many kills with it!

[rootbeercouch]

well i'm going to an ass    and say i told you so,  like three time, that a completely new gear box is what you needed

let this be a lesson to all of you ! when the rootbeer speaks listen! 

[GI Joe]

Yeah yeah, I usually would've known to listen to you root I was just trying to go the cheap route.  It just kept seeming like the problems on that A&K box would be easy to fix, but after ruling out the wiring, battery, and shim job... it became obvious that the box was just doomed.

Aside from some shims, basic wiring supplies, and several nights of frustration... I don't really consider the experience a complete loss.  For the first time in my airsoft experience, I had just cause to bust open a gearbox and really learn how they work.  I've become confident enough to do my own upgrades and repairs now.  When I received that JG box, I knew exactly what to do to swap out that air nozzle and was able to snap the box back together on my first try... something I could have never done before taking apart that A&K box so many times.

Anyhow... that said.  Rootbeer was very right... I could have definitely saved myself some heartache by listening early on.

[rootbeercouch]

it is good you learned all of that joe, very valuable skills you now have

[Hernibal]

?....Yodacouch....?

[GI Joe]

So, I finally got around to using the good ol' "poor man's" chrono ( http://www.airsoftretreat.com/reviews/showproduct.php?product=71 ) to guesstimate the FPS with the new gearbox.  While I can't get a perfect read with it, the FPS seems to be between 340 and 380 (with pretty good consistency).  Not quite what I expected considering the box was supposed to come with an M120.  It's shooting pretty well right now but I probably will upgrade the spring at some point.

[Bishop]

A Systema M120 is rated to around 380fps, however a Systema M120S is rated to 410fps typically. It's a fine point, and I don't know why Systema did this, but not all Systema M120 springs are created equally.

[Northern Lights]

With a good air seal and a tightbore barrel you should see 410-425fps off of a Systema M120. I have done this countless times with both M120 and M120s springs. Unless this FPS difference has been made in the past 2 years(the last time I bought an M120) it should still be the case. The S is a shorter spring with all active coils for systems with a bearing spring guide and a bearing piston head. With the standard Systema length spring you could lock the mechbox due to the spring being completely compressed and there still being a tooth or 2 left on the piston to complete the firing cycle.(VERY VERY BAD) This was not an issue in the early days of airsoft because these aftermarket parts simply did not exist and then when they did come on to the market it was in small batches. The old M120's had inactive coils that could actually be cut off without loosing many fps and allow you to use the two bearing parts. Most springs that I have seen on the market these days are the shorter style with all active coils.



Lights out

[GI Joe]

I doubt it's a Systema Spring anyhow.  JG probably uses their own proprietary springs.  It's hard to tell without an actual chrono, but I'd say it's definitely under 400 (between 340 and 380 is my guess) and that's with a 6.03 tightbore and double o-ring air nozzle.

EDIT:  By the way, how do I tell if my air seal is good?

[Northern Lights]

Sounds like its lacking a cylinder lube job and/or has a piston "O" ring that needs to be stretched. You can do this by stretching it around the cylinder and heating it lightly with a lighter to help keep it stretched. Then put it back on the piston head and re-lube the "O" ring and cylinder with silicone grease. You should be able to create a seal so tight that you cant compress the piston when you cover the cylinder head nozzle port.





Lights out

[GI Joe]

Hmmmm, good info.  I still am not convinced that it's actually an M120 in the gearbox though.  Hell if I know how to tell the difference though.

[Bishop]

Something you can do to check your air seal with your cylinder out of the gun is to lube and assemble the Piston/Head/Cylinder/Nozzle together. Put the tip of your finger over the nozzle to block it and try to push the piston into the cylinder. If you have a good seal you shouldn't be able to push the piston in very much and it should stay that way until you release pressure on the bits. If you have a leak you will be able to push the piston into the cylinder, and the faster it leaks, the worse off you are.

[Northern Lights]

I had just posted that but it is good to hear it again in more words.


Lights out

[Bishop]

Had m' blinders on.