[Cheese Man]

Firstly, clean the hop up unit inside and out, and grease everything. Next, wipe all the grease off the inside of the hop chamber. Then, clean your bucking as per my guide (linked in my sig). Then, if that doesn't work, get a shorter barrel, the stock length is 495 mm. Much longer than that and you may be needing a bore up kit.

.3 is just about right for around 550 fps and a PDI hop chamber. I used .32s in mine...

 

[Cheese Man]

My guide doesn't explain the hop up chamber. What I do, is to wipe it out with a rag, until I can't feel any grease on the inside (white lithium grease ), then, I apply my favorite grease to the inside of the chamber. You have to make sure the chamber is empty first. Then, use your clean bucking, apply a VERY thin coat of the same grease to the OUTSIDE ONLY of the bucking, and out it all back together. Make sure to grease the hop arms too, that can cause issues.

 

[Cheese Man]

Did you put loctite or teflon tape on grub screws that adjust the hop arms? That may be an issue in the future, or right now, so I would try that.