I've not tried that trigger. I've a Rock River and Armalite 2 stage. I don't think either gets down to 4 pounds, though... Not the Armalite anyway. I should check the RRA

I put a trigger tech adjustable into one lower last week. I'm a bit ambivalent about it thus far. Still feel comparatively heavy, despite being set to minimum weight. That could be due to the thin blade. Maybe I should look for a shoe for it.