The Lynx and Cheetah gas regulator is located at the front of the gas system under the front sight post.
When looking and/or adjusting the gas regulator always be sure to follow safe firearm handling by ensuring that the shotgun is unloaded and the breech is clear using the bolt hold open and a safety round or other chamber blocking device!
There are 4 settings for the gas regulator, These 4 settings are identified by the four different size indents on the front of the regulator. These indents should line up with the locking detent located at the 7 O'clock position on the gas block. The four positions are as follows: smallest dot = basically no gas, no rounds will usually cycle when the regulator is on this position. Next smallest dot = "00" buckshot, high velocity rounds and slugs. Next to largest dot = all things in between your results and field testing will be required to see what your individual shotgun will run in this setting. Largest dot = birdshot and other lower powered ammunition.
To change the regulator setting depress the detent using a pick, small screwdriver or similar and rotate the regulator clockwise, if possible, to the desired setting. Always try and keep the regulator screwed in as close as possible to the gas block to maintain as small a gas chamber area as practical.
It should be noted that some ammunition will not cycle a semi automatic magazine fed shotgun. There are some #8 & #7&1/2 that simply will not cycle these shotguns. Winchester Universal & most rounds that are labeled "Target Loads" and similar cheap bulk pack ammunition will not work frequently. There are also some "roll crimp" "00" rounds that will give you failure to feeds and failure to eject as well. If a setting doesn't work for you try some different ammunition before assuming the shotgun is at fault.