A 4 set of rocket valves allowing different flow thus reducing the muzzle energy. I measured FPS and Joule on 20°C (68 F) with 0.2g bbs. With the original rocket valve I shoot around 1.35J. From there I was able to reduce power to 0.9-1.2J depending on the valve installed. This way you are able to choose the FPS/J on a scale according to your needs/local rules. I added 0.1J to the measured J value to make sure it's not stronger than the indicated value (with 0.2g bbs on room temperature). So I measured the '0.9J' indicated rocket valve to be 0.8-0.85 J and so on. I need to underline that the KWC mini uzi has a lot of Joule creep, so heavier BBs will have more energy than 0.2gs. If you want to use 0.25-0.28g bbs and still be around-under 1J, you need to use the 0.9J indicated rocket valve. There are two versions of output valves on the magazines, If you are shooting above 400 FPS out of the box than there is a good chance you have the high flow output valve on your magazines. In that case, the indicated J values increase by about 0.2-0.3 J for all of the rocket valves. You can overcome the output valve difference altogether with my
adjustable gas flow loading nozzle:
I chose PA 11 as the default material because it's more impact resistant than PA 12.