Hmmm, what's wrong with this mechbox?
 

So, I had an SR-16 fully upgraded mechbox fall into my hands. Previous owner had sent it to a mechbox mechanic recommended by a friend of his. Seller barely used it after upgrading, said he dry fired a few shots then it stopped firing, figured the battery was dead so he packed it away for a few months then sold it. Anyways, check out the things I found and see if you can figure it out for yourself. There is one really obvious one, one barely noticable one (but serious), and one that I won't even bother asking you to find.......... there are ONLY two shims in the entire mechbox!!!

http://warmongers.dyndns.org/albums/...hbox.sized.jpg

:cry: My baby... look at the horror :cry:

Oh oh i know but its cheating if i reply

Yes, neither of you are allowed to play this game.

What's that Allen key sticking out of the spring guide and your cylinder is backwards.

I know next to nothing about internals but I'll just take a guess.

Isn't the cylinder supposed to have the hole at the back? (away from the nozzel) If it's that far forward you'd get next to no compression right?

Bruce, the allen key was used to hold the spring while I separated teh mechbox halves, keeps the spring from shooting out.

And yes, the cylinder is backwards. BUT, all the M4/SR-16/733 I've worked on, I don't recall any of them having a ported cylinder. My MP5 does. Ported cylinders are for short barrel lengths.

Keep looking for the small yet hysterical other.

My ICS M4 has a ported cylinder, but it's tear drop shaped.

Hmm, ok. I might not have noticed on some of the cylinders I've dealt with, but everytime I saw one I used to wonder "Why on some and not others?" Need to get MadMax or Illusion to break out their comments.

Just used the "Vondnik Shim Technique" and found the sector gear is set up nice, but there is a 0.5mm movement with the spur and bevel gear. Not comfortable with it, prefer a little less, but I guess we can't fault the guy for a reasonable job doing it.

OMG ppl I noticed the Small insignificant but hilarious other issue and I have
never seen the inside of a mechbox...

looks like the spring on the reverse pevention latch is turned the wrong way.....also... the box generally has way to much lube in it... and only 2 shim in the entire box isent good either.....
is there no theeth on the middle gear? kinda looks like the nozzle guide is snaped in half also.....

Anti-reversal latch spring is out of place?

Bingo, we have winners! Anti-reversal latch spring was installed backwards. You can see the part that is supposed to be on the latch itself is actually sitting overtop the wires.

http://warmongers.dyndns.org/albums/..._003.sized.jpg

Nozzle guide is fine, tappet plate is fine, grease is about normal from my experience (and as I tend to do it as well, without overdoing it.)

so does that meen im suposed to put THAT much lube in my gun?
cause if so, i have been horibly under lubing my mechbox.

Need enough to keep things running smooth and lubed, without huge piles of liquid grease getting everywhere. Worst place to get grease going (aside from into the cylinder if it has the chance and blowing out onto the hop up and barrel) is on the contacts, reduces and eventually can cause lack of current flow, making your gun stop shooting. Might be a tad too much in this gun, but once I get it all back together again, there will be less in the box and more on the rag.

Edit: Ok, there IS too much in this, just found a BB sized glob under the sector gear. Having it on the gears like that is ok, but having large globs elsewhere isn't. Add in too much on the piston too!!!

EDIT Again: Found the little block right behind the trigger contact block (keeps the block from moving too far back) has broken off as well. Noticed this in Apoc's G&P SPR, thought it to not be much of a problem, until his gun jammed up. In this case it doesn't seem like it'll cause too many problems, but in the SPR, it's a lot stronger spring, ended up angling the block upwards and it jammed on the bottom of the tappet plate.

That is so much lube. Actually too much lube specially on the cylinder is not good. Excess lube goes out the nozzle during compression and goes to the chamber and if not cleaned regularly lube becomes sticky and BB's will get jammed.

At first glance, I'd say at least that your cylinder is backwards. The port is supposed to be closer to the rear. IRC the SR and other M4 variants put the port pretty far rearwards. Only the very short barrel AEGs put the port close to the middle. I don't think any put it that far forward.

It wouldn't be the cause of your electrical issues, but you'd certainly not push enough air.

Carl, you read the latch spring was improperly installed as well?

Ya, huge noticablility with the port on the cylinder. Is why I pointed out it'd be an easy one. Hazard decided to buy a new cylinder and head for it. Otherwise, even after jamming up, everything is cool inside the mechbox.

I glossed over that one as I thought that the issue was resolved.

Certainly looks gooey in that mechbox. It's often not too much of a problem though if you make sure that they cylinder window doesn't open towards the inside of the mechbox. It should point outside to prevent grease from getting into they cyl thru the window. I like to wipe down the inside of a cyl before reassembly leaving only a very thin film of lubricant. Too much grease eventually finds it's way around the oring and gets to the inside of they cyl and gets blown into the barrel.

I found after removing the piston a huge glob of grease on the sides and head of the piston, so I wiped it all off and left a bit on the O-Ring of the head. Found, as I said, a good amount of grease all around the selector toggle (under the sector gear) and it was enough if not more than the size of a BB. Basically I took off all the excess grease from the areas that no mechanical contact comes itno play. Also spent a bit of time clearing the black crap off the contacts the trigger block runs into (totally unsure the names of contact parts. Never had to talk or discuss them before).

All is back together, when I get the chance I'll run it through it's paces. Hazard told me there was a good chunk of lamp cord in between the small connector that attaches to the back of the receiver, and the large battey connector that connects to the battery itself. I think I sorted it out to give extra length to the cable to allow easier battery hook ups. Will do a better rig/splice for that.

Since you are here Carl, might not be a bad idea to link this thread to the one you did on the ported vs. non-ported cylinders in relation to barrel length. Since it got brought up a few times here, why not? Was an outstanding piece you did! Even if a little hard for average minds to follow. ;)

Every single stock & virgin Marui and ICS M4/M733/SR-16 gearbox I've worked on had a ported cylinder.

Guess Apoc's 733 is an oddball then, it has a full cylinder. Like I said, I've worked on all the variants, but never really noticed porting vs. non-porting.

Update ont eh mechbox, as I was reassmbling it, I noticed the trigger retrun spring was also missing. Go figure, it was included sperately in a small bag of parts. Guess the guy had it as a left over, didn't know where it went so just included it with a light bulb, a few extra screws and whatnot. Glad I can work on mechboxes, cuz I'd hate to have this guy work on my internals!

My SR came ported. So do most AEGs that are under 590mm barrels if im not mistaken

Ok guys, thanks for the info, I'll stand corrected now. I think the last M4 I had come across my bench was back on the fall, and prior to that were M4s, the 733 (with full cylinder, 100% of that because out of curiousity I tried it in my MP5, found my fps went down by 30fps, switched back), SR-16s, etc. So recently just did some more work on the 733 (changed new internals over to the reinforced mechbox), full cylinder still there, and a G&P SPR last week. Guess I assumed the TM 733 had a stock cylinder in it, is the shortest of all the Armalite inner barrels, so anything over that length had full cylinders, and anything under that length had ported. Just begs the question: If the stock 733 had never been opened before me, how did it get a full cylinder? Might explain the wildly fluctuating fps readings (360-390fps) we got last spring with it.

so where in the mechbox those two shims are located when you saw it??

The shims should be on the gears.. hahahahaha

Thanks, but this thread is over a year old.