Gremlins or cursed?

[HKGhost]

Here's a riddle for you guys to wrap your noodles around.

Gun is a VFC M4 with mostly stock parts other than piston, piston head, cylinder head and cutoff lever. Complete V2 gearbox outside of the body with the motor installed works fine. Trigger pulls cycles the gearbox is semi, full auto and locks in safe. Normal right? Install gearbox into the lower receiver, can't pull the trigger back in safe, semi or auto. Puzzled? Removed gearbox and the trigger pulls back in semi and auto again. Thinking something moved or shifted during install, I tapped down the selector, cutoff and safety lever in the full auto position just to check. Reinstalled and trigger is locked again. Trigger isn't making any contact with the lower receiver or anything other than the gearbox.

Cutoff lever doesn't protrude out pass the selector plate or making contact with the body. So it's not that. Trigger works fine out side of the body, but once installed, the trigger locks like it's in safe mode. Gremlins playing tricks here? I had the owner and his friend witness this and all of us are puzzled. It doesn't make any sense. Gearbox installed into the lower has all it's pin holes line up like it should. Nothing is moved during install or shifted. Anyone with a hypothesis on the cause?

By the way, this gun has been full of headaches and problems one after another. But those stories are for another time.

[Danke]

My VFC 416 did something like that once. I'll let my subconscious try to pull up how I fixed it. It might have been the selector disc over-riding the plate.

[Stealth]

Swap selector plate and trigger.

I'll go into more detail if you can't figure it out.

[Cliffradical]

Follow Danke's advice first.

I've encountered irritating garbage like this numerous times (even with VFC), and head vs brick stuff like this is often the last thing you'd look for, but tooth-grindingly obvious after the fact.

1- Are you %110 sure that there's nothing catching on the body? Even if everything looks fine to the eye, the cutoff lever can stick on the most ridiculously unobtrusive bit of flash or mould line existing on the body, especially if it's aftermarket or interacting with different spec (non-stock) gears. My most recent selector issue was due to this.

2- Did you remember to replace the spring on the plate? Everyone forgets this once in a while.

3- This is a wild card, but are you sure the trigger is stock? Is it sitting correctly? When a trigger contacts the trigger aperture in the lower receiver even the tiniest little bit it can throw the whole system off. Think of the ridiculous angles created by a small amount of pressure one way or the other. This is more of a problem in MP5s but I've seen it in VFC Armalites as well.

4- Did you pray to the Machine Spirit? Recite the incantations of re-awakening thrice and the blessings of Mars once and ye shall find great solace or great pain.

5- I bet the cutoff lever is catching on something you can't see with the mechbox installed in the lower. Scour the opposing inner face with a fine file or sandpaper and give the cutoff lever's outer post a once-over as well.

[lurkingknight]

check the selector switch and the cam, it could be stripped and spinning free.

[HKGhost]

The fire selector moves freely and isn't riding over or out of position on the selector plate. When installed, you can rotate the fire selector into all three position effortlessly, and the selector plate also moves into all three position. The gearbox isn't tight, binding or in some places, even touching the lower receiver. As soon as the gearbox is seated into the lower with all the pin holes lining up, the trigger gets locked. Partial install into the lower doesn't lock the trigger. Only when it's completely seated and in position like it should be, is when the trigger locks up. The cutoff lever isn't protruding out pass the thickness of the selector plate, so it's making no contact with the body. The spring is installed and also moves freely when installed. After testing it with the masking tape locking everything down, the trigger still gets locked up once installed into position. In the full auto position, there should be zero restriction and the trigger should move freely. But even that position is locked once installed.

I'm gonna be trying a new selector plate in hope to fix this issue and another. This gun has been full of gremlins and only works when it wants to. I'm very experience in working on AEGs and have worked on at least 200 V2 gearboxes, and this is the first time I've came across this. Never heard this happening before and especially not to a VFC gun. Total mystery.

[Stealth]

Wait I just re-read your original post. Initially it sounded like something I just worked on, but after reading it over, I would suggest swapping out the safety lever if your trigger is actually locked.

Presumably when you say your trigger is "locked", it's immovable in any of the 3 positions?

[lurkingknight]

could it be that the lower receiver pin when inserted is pushing a trigger wire into the path of the safety?

[HKGhost]

Originally Posted by Stealth

Wait I just re-read your original post. Initially it sounded like something I just worked on, but after reading it over, I would suggest swapping out the safety lever if your trigger is actually locked.

Presumably when you say your trigger is "locked", it's immovable in any of the 3 positions?

Yes, when the gearbox in sitting inside the lower, the trigger is locked as if it's on SAFE, but in all three position. Once the gearbox is pulled out of the lower, everything is normal again and the trigger can be pulled like normal is the two position. To confirmed nothing was moved during the install, I've taped down the whole left side and leaving only the round section for the fire selector. Even then, the trigger locks once installed. Only things that can lock the trigger is the cutoff lever and safety lever. Safety is locked in place with making tape is the fire position. And the cutoff is locked in place with making tape in the full auto position. Trigger pulls normal out of the lower and locks once installed. The wires aren't in the way of the trigger as if it was, then when the gearbox is out, it should do something with the trigger, but it's all normal. And most of these parts are stock which all worked before.

[Danke]

Take us back further. What sparked this situation, what parts changed, and when?

[Cliffradical]

We need to go deeper.

[JDoorn]

put the pins in the gearbox outside of the lower and test it, at least you can eliminate the pins causing the problem...

[Cliffradical]

Wait wait wait, banghead nanny check:
Are we absolutely sure that the spring for the safety lever is correctly installed? Is the lever itself catching on any part of the body when installed?

[HKGhost]

Originally Posted by Danke

Take us back further. What sparked this situation, what parts changed, and when?

Parts changed are in my first post.

[HKGhost]

Originally Posted by JDoorn

put the pins in the gearbox outside of the lower and test it, at least you can eliminate the pins causing the problem...

Pins in has no change. I don't even need to install the pins when the gearbox is in the lower to have the problem. Pins in out of the lower doesn't affect the gearbox, and it works like normal.

Originally Posted by Cliffradical

Wait wait wait, banghead nanny check:
Are we absolutely sure that the spring for the safety lever is correctly installed? Is the lever itself catching on any part of the body when installed?

Lever isn't making contact with the body at all. Like I said, when installed into the lower, you can rotate the safety lever to all position without issue. But the trigger is locked as if it's stuck in safe. Out of the lower and it works as if nothing is wrong.