Empty the gun of air, unscrew the airtube, unscrew the brass valve, push reg in (lube orings first), screw in valve, screw in airtube, fill with air, check chrony, repeat if needed. You'll have to pull it all back out to readjust. http://www.altaros.cz/en/hatsan/18-regulator-hatsan-at44-hammerli-pneuma-elite#/|demoTab2 dunno what brand you have but they are all pretty similar
Has anyone here installed their (Hatsan's) after market regulator? Has the velocities/ES been more consistent? Has shot count increased? Did you leave the setting as it came or did it take some fine tuning (removal/resetting)?
1. yes, 2. hell yes, 3. not from the same fill pressure down to the regulated pressure, but the reg allows higher pressures in the tube, thus more shots in that respect, 4. no it took maybe 4 goes to set it where I wanted