There are certain powders that are better suited to "gas guns" like the AR.
The good news is there are plenty of them...its not a short list.
I use Reloder 15 in my AR loads.
Its best to crimp the bullets...some people refuse to do it, but I know from experience that an AR 15 beats the heck out of a round during feeding, just look at the ejected brass...besides the dent on the shoulder from bouncing off the deflector, it will be nicked and dinged in several other places 90% of the time. The feedramps "deflect" the round (sorta), which is a good place to get bullet setback with loads that are not crimped.
Opinions vary greatly on load data... I have some recipes for 5.56 NATO spec ammo (way too hot for a 223 Remington chamber)
I also have some decent varmint loads, all of which use Reloder 15 except 1 (that one uses AA 2230)