Full auto not working.

[Adamlxlx]

Hey guys,

So I am putting together an m4 scratch build. I have got the mechbox together no problems but am having a problem selecting full auto. I think I know what it may be but I need more input.
Basically the gun shoots semi no problem. When I put the selector to auto the trigger is locked like it is on safe. The mechbox is sans a safety unit at the moment so I know it is not that. My selector plate moves fine, no binding. I am not missing the little spring either.
Honestly I think it is a shitty mechbox. The bushing that the yaw adjustment bar goes over sticks up a bit due to a shitty cast. They are 8mm bushings and the one for the sector gear sticks out a little on the inside. Could the arm be binding on this non flush bushing causing my full auto to lock and not work?

Thanks in advance.

[Boyso]

Have you tried moving the selector arm manually when you have the left side of the box in your hand? You'll see real quick if it's binding on something.

[Adamlxlx]

Thats the funny thing, it moves smoothly outside the gun. When I open it up and move the arm it is not smooth. Its confusing me.

5 minute later update: So with the mechbox out of the gun with just a pistol grip and a motor the single/auto fire work fine. As soon as I put it into the lower the full doesn't work. Could the selector plate be binding on the inside of the metal body? I am using a dboys m4 body. Fitment isnt terrible but maybe I should file it down a little on that side?

[voorhees -FWA-]

Try to put the front pin in the upper and lower receivers, so it pivots. Slowly try to close the body and watch the selector side to see if it is binding on the body. Mark any place that the upper receiver contacts the selector arm. You can try to remove some of the inside of the body to get the fitment right. The movement of the switch should be smooth; so there is something binding in there.

[DarkAngel]

If your symptoms are what you say "ie. Trigger locks on safe" and the Safety Lever has been removed, the only things that could possibly affect your trigger would be the wiring shifting to block your trigger or the 2nd half of your Contact Plates. Otherwise, nothing else would be able to stop it.

Selector plate movement wouldnt cause your box to lock if there is no safety unit attached. (Im assuming you are talking about V2 box here)

Dboys metal bodies are VERY low end brands (sorry but its true). They have been known for many years now to have fitment + tolerance issues. Im not saying that this is the particular case in this situation as I cannot see the gun in front of me. The only issue I have with your statement re: sans safety and it works fine out of the body, is that they contradict each other. The body would have no affect on the gearbox without the safety latch installed.

A more common and likelyhood scenario would be that the safety latch is too thick, and the tolerances of your Dboys metal body (QC on dboys is utterly shit, no two parts come out alike on Dboys) are pressing against the safety lever.

One of two things can be done in the above scenario.
1) File/dremel the body (a small recess) where the safety latch is.
2) file down the safety latch

[Adamlxlx]

Little update: I understand dboys is shit but it does not work in a TM lower either. I am using a shitty selector plate maybe that is it? Its just a stock white plastic jg plate. Other than that I am out of ideas

[audi_bhoy]

Well if it works flawlessly outside of the lower body, and doesn't once inserted in a lower body, the issue can't be elsewhere, it's a GB/Lower body issue. You'll have to use some dremel to oversize your body where it stucks with the selector plate. Not a big deal if you know what you're doing.

[DarkAngel]

Again. Selector plate does not affect a gun with no safety latch. If the trigger is locked and unable to move even without a safety latch, then putting it in a body will do nothing to cause your problem.

Please test your box again. The symptoms you've provided are contradictory and not sufficient

[Adamlxlx]

Contradicting or not.....it is happening. Simply put with just the pistol grip on the gearbox it work, single and full auto, no binding of the plate or yaw bar. I have tried putting it in my dboys lower AND a tm lower yielding the same results. Shoots fine on semi and then either has trigger lock in auto or shoots semi. I am at work right now but i will post a video tonight so you get it.
EDIT: Darkangel i dont think you understand what is actually going on. I may have worded it incorrectly. Everything works outside the body. The trigger is fine. The trigger only lock/binds when it is in the body on full auto, semi works, it is just when i put it into the lower body on full auto.

[Adamlxlx]

Fixed! It WAS the selector plate. As soon as I switched it out for a TM one it worked.......

[DarkAngel]

Yeah, i really am not sure what you were saying. Thing is, without the safety latch, there is nothing that physically blocks the trigger with a solid stop. You can get wires that get in the way, but they have a tad bit of give when that happens.

I think perhaps you have the terminology down wrong. This is a safety latch.

No safety latch = no stopper arm. No stopper arm = nothing to block your trigger physically.
Regardless of anything else on your gun, if you dont have a safety latch, nothing will stop your trigger from moving.

[Adamlxlx]

My terminology is fine, you are just not reading it right. I love how you assume you are always correct, good attitude. If the cut off bar on the inside is jammed or too tight it can provide a sticky trigger. You can say whatever you want but i have seen it on more than a few gearboxes not put together right. I thank you for your attempt at helping me, no further reply is needed. Thanks again.

[audi_bhoy]

Well the cut-off lever can act as a trigger block when passing from semi to auto, that moment is as thin as tooth's skin but it is still there.