Screw
Hi Steve
It translates as "screw pin" so not a lot of help on that, its certainly not a regular adjustment and there is an air way under it which is why you lost power. If you screwed it too far down it could restrict that airway so it could be some form of fine air set up
I've measured on mine and it's set at a depth of 3.5mm from the top to the top of the screw so I suggest setting it to the same. As there is an airway under it I'd be very carefull using loctite and be sure you get it only on the top threads of the grubscrew so you dont push any into the airway.
If you want to know definitively ring Harry.
Best of luck.
Robin
Walther KK500 Alutec expert special - Barnard .223 "wilde" in a Walther KK500 Alutec stock, mmm...tasty!! - Keppeler 6 mmBR with Walther grip and wood! I may be a Walther-phile?