Have you attempted any of the mods to your stock FCG?
Polish all the contact points.
Cut one of the "tails" of the hammer spring.
Bend the trigger spring tails "up"
Set screw through pistol grip to stop creep.
Cut hammer into "speed" hammer.
I did this to my bushmaster, and if I had to guess I would say it's around 3.10lbs, or around there. Almost no creep at all. I use to have a JP adjustable trigger w/ speed hammer and my modded stock trigger is maybe just a little bit "harder" but that would probably change if I got JP yellow springs.
I still used the upper w/ a .22 kit and it functions fine.