VFC HK416 small trigger/selector problem when top receiver is on.

[EscapisT]

Hey guys,

My vfc Hk416 is ready to go...KA Helical gears (nicely shimmed PITA), madbull 6.01, guarder silicone hopup, kingarms metal hopup chamber.... Everything works great but I have a small trigger problem...

When the top receiver is off, the trigger and selector function as they should. However, when attach the upper receiver (slide on & pin style), the trigger and selector don't function properly:

-SAFE IS NORMAL

- SEMI -
Instance 1 - (Trigger is hard to press - "Clicks" at first - Then works fine -after switching from safe.
Instance 2- works perfectly when switching from full to semi)

- AUTO - Lastly, when on auto, the trigger doesn't budge as if it's in safe.

I would be led to think that the problem lies with the selector assembly or perhaps the trigger block IF it didn't function at all. But it works perfectly when the top receiver is not attached which completely baffles me. There is no point of contact between the upper receiver and selector assembly as far as i can see, yet somehow it causes it to malfunction.

[Danke]

Check the disc on the safety lever, make sure it is tight. Check the selector plate that is is moving freely, check the safety switch, and check the cut off lever.

So start at the safety and check over every moving part between till you're fully in the gearbox. See if any of that is loose, damaged, knocked out of place.

[EscapisT]

well, checked everything.... Disassembled the trigger block completely as well as the selector assembly... put it all back together as precisely as I could. Checked everything for damage or wear. no cigars. Reassembled, Issue still persists. I have no clue what might be causing this. How can the upper receiver possibly mess with the selector assembly? Upper receiver on, it messes with my trigger/selector... upper receiver off and everything works as it should.

Pigs must be flying today or something cause my logic is completely wrong, apparently!


Details: I slid the upper receiver on and checked the trigger at every 1cm increment. It starts to affect the trigger once it hits the last 1/4" or 1cm before it's completely slid in and aligned to pin.

[Danke]

Something is binding up, I had the same thing go down with mine and it was just a series of little things that once the extra tension was on the box when it was fully built up it would not run right.

Mine came used with non-stock upgrades and somewhere along the line there were one too many changes. It works great now but it was a lot of late nights and taking it apart again and again till it got to that place.

I would hunt up a gun Doc who's been in the game 5+ years and see what they can spot.

[EscapisT]

I do know someone who's really good with aeg's. I guess Ill just bring it to him, although I do enjoy learning about these things. This thing is just killing me.

[EscapisT]

Well, fixed it!

Turns out, the rear end of the selector plate (where the selector switch disk engages) was bent.... I remember it being like that out the box.... Bent it straight and the trigger is as smooth as glass.... This thing was just a heap of problems the moment I unboxed it.

The helical gears are nice, but somehow louder than the stock spur cut gears. I know they're shimmed impeccably; Gearbox closed with screws, I can get 5-7 revolutions free spin, and about 0.01mm of lateral play AT MOST. This has got me wondering... I read threads where people are saying helicals are much louder, and others saying they're quieter. Wikipedia, believe it or not, says helicals are quieter than spur gears.

What gives?

Furthermore, I'm getting a small motor problem again. Sometimes the mechbox would "lock" up at the bevel and pinion (famous "fire and click" noise as if battery was dead)... I would remove the motor plate at the bottom of the pistol grip, hold the motor down manually, fire, and that would cycle it and in turn unlock it. I'm not sure if it's motor adjustment... I played with it a little and I just got 100 rounds through it with no hold ups... but I have a skirmish tomorrow so I dont want to run in a fire fight with potentially obsolete tools.... Can it possibly be bevel shimming??? Narrowing it down to the motor height would just make life much easier for me right now since ive lost count of how many times ive opened the gb up.