Winchester 52B trigger adjustment

I have unscrewed the screw that is accessable from the top when the bolt is removed, and got my trigger pull down to about 3 lbs. If I set it any lower with this screw, the hammer follows down when I close the bolt.

Does anyone know how to adjust this so I can have a lighter pull? I'd like to be in the 1-1/2 to 2 lbs range for bench shooting.

Thanks!
Arden