WE HK416 Problem
 

I have an open bolt WE HK416 and what's happening is when I cock the rifle, I only get one shot and the bolt closes. It basically is acting like a bolt action gas sniper rifle. Anyone ever hear this?

your nozzle is broken.

No it isn't. I have an aluminum RA-Tech nozzle and I carefully inspected it, it's fine.

Valve knocker or delayer. Something in that area.

We got it cycling through one entire mag... than it'll do the same thing over. We've swapped out the nozzle, bolt carrier, and even the trigger group with brand new stock parts and it does the exact same thing. It was shipped over from BC, we're thinking something got misaligned during shipping.

If something is misaligned, wouldnt the bolt already have trouble moving? You say you get one shot out of it and the bolt goes back to idle position, and plus you cycled it through one mag. Maybe it has something to do with the safety lever or whatever part that interacts with it? A video would be helpful maybe?

Your firing pin may be too large if your body is out of spec. Sometimes you'll charge the rifle and get one anemic shot out of it. Sometimes you'll hear a loud clank but nothing. Sometimes it'll shoot fine. I had an issue where my lower was out of spec and the pin was a 1/2 mm too long, getting caught on the magazine if I didn't cock the gun before loading.

Well we got the gun firing... a single mag, then right back to what it was doing. What's strange is that when the barrel was loose from the gun, it would function properly with a stock nozzle. Now we're seriously fucking confused.

Now it fires, but we had to shim the hop-up unit guide and use a stock nozzle... :|

I had a similar issue with my G39. My wheel on the trigger group, in contact with the bolt had broken (Pin was broken, the wheel fell off). No more wheel, the hammer (I think) was scratching and blocking the bolt from moving.