Henrik,Hey, hameditor. TY for opening this Community! I live in Denmark and my PCP equipment consists of a Weihrauch HW44 pistol and a brand new Diana XR200 OD rifle. The rifle has an ajustable regulator with a screw on the left side and a manometer on the right side. According to the manual turning the screw counterclockwise will increase the energi and vice versa. But there is no further information so I´m a little doubtful about setting the regulator.
We reviewed the XR200 recently in HAM, maybe you've seen it here Diana XR200 PCP Air Rifle Review .22 Caliber - Hard Air Magazine
You are right, the screw adjustment on the left side of the breech can be used to alter the power output of the gun. But it is - in fact - a "transfer port adjuster" and not a regulator. The regulator in the XR200 is set at one fixed pressure in the factory.
In simple terms, this means that adjusting the screw on the left side of the breech allows more or less air to be effectively applied behind each shot. You can experiment with different settings without fear that you are changing anything permanently. No problem!
I hope this explanation makes sense...