Does anyone have any information on the real-world adjustment range of the Daisy/Avanti 747 trigger?

They say, or imply, that it should be adjustable down to 1 lb or less, but I am not achieving that.

I bought a 747 after acquiring my father's nearly pristine 1970's-era 717. I wanted to get a 747 for the adjustable trigger, as the 717's trigger felt kind of heavy. I've adjusted it all the way up and all the way down, and there is a perceptible difference, but it is slight. Today, I finally received a real trigger pull scale and it proved what I suspected -- the trigger pull weight is adjustable from about 5 lbs down to about 3-1/2 lbs. Is this what it is supposed to be, or is something wrong with my gun? How far out should the adjustment screw turn? I noticed it does not come out very far at all, as I can still see easily 3-4 turns of threads above its top surface when it stops turning counterclockwise.