On the 22/45 I have has the trigger down as far as 1lb. I had to do extensive work on it, adding an adjustment screw to limit take up, etc, and to shim the sides of the trigger to limit play. at 1 pound it had a propensity to double tap, so I brought it up to 3 pounds or so. I really do not think that they are meant to go this light, there is too much slop in the system for a consistant trigger pull, and the stock components are suseptable to excessive wear when stoned down to get a lighter trigger pull.
the adjustment on the trigger for these things is on the trigger itself and it needs to be removed to be adjusted. It is just to limit over travel, and is a little allen screw. it is a pain to get to and required tearing everything down.