I have an RRA 24" stnls bull barrel upper on a standard Bushmaster lower. My intent is for this to be a Varmint gun, but I want a lighter trigger than the standard Bushmaster lower trigger. Does anyone have any experience with some of the drop in targe style AR triggers? I'm looking for some thing that will break nice and clean at about 3 lbs. I've considered Timney and Chip McCormick drop ins. Anyone with experience with these? Any others you would recommend? Drawbacks on any of them?