Junk Yard Genius.com AR-15/M-16 Pages, page 1.
The design of the AR15 hammer - why the notch, why the tail? - AR15.COM
And of course polish the contact points(I start off with 600grit wet/dry sand paper, and finish off at 1000 for a shiny finish. Take your time and use a flat board/surface)
My most used AR is at 3.10lbs. And I've used it on my .22 for about 4k rounds w/ no issues. Only the occasional dud round.