This is a new build with a suppressor. I need suggestions or help. Ok it's a 12.5" Novesky barrel that a reputable company cut down to 11.7" for me. The gas block is an SLR 7 gas block at 6 clicks the bcg locks back unsuppressed and even loads a round, so I set it at 7 clicks and it functioned flawless. Next I installed the suppressor and the gun fires but the bcg seems to lock back partially some how sticking on the empty magazine not the bolt release. Oh and I'm using a jp low mass bcg with a jp silent capture spring. So I started with the weakest spring for the jp scs and like I said unsuppressed I get it working flawless suppressed it appears to short stroke and lock back on the empty mag not the bolt lock. I literally worked my way up to the strongest spring for the jp scs and I'm still being it to only lock on the magazine. Every new spring worked unsuppressed once tuned. At one point I almost had the gas block adjusted all the way out. The only thing I didn't try was turning the gas block down lower than 5 clicks. Because unsuppressed the bcg would not lock back at 5 clicks

Things I didn't try, a different magazine or a normal but and carbine spring.

If I'm missing info let me know.

If it locks back during a mechanical function check, there's nothing wrong with the buffer and carrier setup.

If it fails to lock fully during live fire, it's either a short stroke, or a fast stroke - short is remedied by more gas or less mass, and fast stroke by less gas or more mass.

I can't tell if it's short stroking or moving to fast.

So normally the bolt locks back on the bolt release once the magazine is empty but what happens when I go suppressed is that the carrier is locking back on the bolt release and the bolt is slightly forward. So if you are just looking at it after it been shot empty it appears as though the bcg didn't go back far enough.

Adding on the suppressor should increase gas pressure right? So I figured if I set it up to run unsuppressed it should run suppressed fine theoretically? Is it even possible that once the suppressor is added that it becomes way over gassed and everything is moving to fast?

I didn't notice a tone of gas in my face. It was also hard to tell the direction my shells where ejecting.

Something for y'all to laugh about. I had my can on and off a lot. One of those times i must have been complacent installing it and my can was a projectile. No damage other than scraping it up just embarrassment.

That would be my first guess - since the rifle apparently runs fine without the suppressor. With the can it's overgassed, bolt carrier is overspeed, and the magazine lacks sufficient dwell time to raise the bolt hold-open before the carrier has rebounded past it a little bit.

I'm just confused now as much as before. If this is the case wouldn't that mean when I increased the gas that the carrier would then race past the bolt catch? I know it's hard to diagnose a problem over the internet. I appreciate all your help thus far.

I'm going to try adding weight to the buffer as per JP's recommendations. I'll keep you posted.