Hi All,
Once again, I am no expert, but I have access to all three versions of the Impact. In the interest of clearing up confusion created by so called experts (read Matt, not Ernest) here are the differences.
First Impact series:
Pointy reg adjuster, Short piston, 9mm reg body, 11 spring washers of which two are black and thinner than the rest, duro 70 orings.
Second series:
Serial number stamped on receiver, domed reg adjuster, long piston, 9 mm reg body, 16 spring washers all the same, some duro 90 orings, reg body/adjuster and receiver dimensions changed to allow for hole locations and adjuster screw alignment. This config can’t be used on series 1.
X series:
Serial number stamped on receiver, domed reg adjuster, long piston, 10 mm reg body, 11 larger spring washers all the same, some duro 90 orings, reg body and receiver dimensions changed to allow for hole locations and adjuster screw alignment. This config can’t be used on series 1 or 2.
Regarding adjusting the reg, version 2 and version X technically can be adjusted down under pressure, BUT, this needs to be done while the piston is not under back pressure. So fire the gun and turn screw at the same time in small increments to relieve said back pressure.