WE M4 Open Chamber Fire Mode Issue

[MaybeStopCalling]

Recently I had an issue with my WE M4 OB where the rifle wouldn't fire unless I inserted a magazine with the bolt locked back. This quickly degenerated into the rifle going runaway on semi, stopping only when I dropped the magazine. I replaced the trigger group with a Ra-Tech group, and all was well for a week. Today I decided to fire off at a couple of targets. Rifle starts doing burst fire on semi-automatic. I open it up, and inspect the trigger group. Nothing looks like its out of the ordinary. I'm at a bloody loss.

Two thoughts:

1. For some reason the bolt is short stroking and thus the hammer isn't locking back. An NPAS was installed, but otherwise everything is stock. I suspect this may be in part due to the OEM bolt hitting the upgraded parts- I can see a divot in the bolt carrier forming, and a steel carrier is my next upgrade- I'd like to fix this first though.

2. The problem doesn't exist when I firmly pull the trigger back all the way... it's when I creep it back to the breaking point it goes auto when it sits on that breaking point. I don't want to say it's the trigger group since two exhibit the exact same issue. But I'm tempted to throw in a CWI hammer and disconnect and see if that fixes anything.

Any ideas? I'm completely stumped.

[Ballcancer]

check your sear. It sounds like an issue with the sear anyway, as its worn down and not allowing a full trigger reset.

[MaybeStopCalling]

I read on gasguns.info that the RaTech parts aren't dimensioned 100% to the WE parts, so I just stripped out the two trigger boxes I had and took a look. The original disconnect and hammer were okay, then I remembered that for some reason the bolt had kept bumping into the RaTech sear when I first installed it, so I had replaced it with the WE sear. Swapped the original hammer, disconnect into the RaTech box, and also put in the RaTech Sear.

Problem fixed, at least for now. I hope. Doesn't explain why the sear started working when it had kept hitting the bolt in the past though.

[Ballcancer]

Yea it will work for now, but because WE parts are aluminum or pot metal (I can't remember which), and the other parts are steel, they will wear out fast. I would compare each part and then take a dremel and grind the parts down to roughly the same dimensions. It's what I did with my AWSS WE M4 and it worked perfectly afterwords.

[MaybeStopCalling]

If anything, it seems like I would need to add material to the Ra-Tech parts to machine them down... where the WE OEM has straight edges and sharp corners, the Ra-Tech parts have more of a contour. The only parts not OEM in that trigger box are the trigger, the valve knocker, and the sear. I'll keep an eye out for issues and wear, but I guess i'll have to grab another set of aftermarket trigger internals not from RaTech when the time comes.

[turok_t]

Originally Posted by Green Synergy

If anything, it seems like I would need to add material to the Ra-Tech parts to machine them down... where the WE OEM has straight edges and sharp corners, the Ra-Tech parts have more of a contour. The only parts not OEM in that trigger box are the trigger, the valve knocker, and the sear. I'll keep an eye out for issues and wear, but I guess i'll have to grab another set of aftermarket trigger internals not from RaTech when the time comes.

PM sent.