Lines of Effort
So, we all wish we could afford a fancy drop-in trigger pack with a feather release. And, it would allow us to finally shoot our 99% complete AR lower that is working hard as a paperweight due to the slightly (just slightly, mind) incorrectly drilled trigger or hammer pin hole. But who's gonna spend $200 to fix a $75 lower?
We're not. Standard AR FCS pins are smaller than some Colt FCS pins. (Why, Colt, why do you hate us so? Are you secretly in bed w/ HK? Were you infiltrated by zee Jermans?) So standard AR FCS pins sail through Colt FCS parts with room to spare... room to spare for a bushing. At the Feinstein Project, we're fond of bushings...
So, take Colt (or aftermarket for Colt) FCS parts, bushings to fit them, and standard AR FCS pins to run through the bushings. Cut the pins no wider than the INSIDE of the AR lower.
All we need now is a chassis. Not bricks this time. A folded piece of sheetmetal, with holes drilled more accurately than we did on our lowers, that accepts Colt diameter pins. Now you have a drop in trigger pack you can Loctite in place in your poorly drilled/undrilled lower.