ARs vary a lot, depending on twist, and barrel length (not to mention the brass and primer combo you'll be using). Generally speaking, extruded powders deliver better accuracy in almost all the rifle shooting disciplines, but true some ball powders can and do often do just fine. Ball powder does meter "better", but that is a function of your powder thrower, some thrower do far better than others. I'd like to suggest you get a number of loading guides/books (you can never have too many) starting with Sierra's. They[Sierra] have broken down loads for bolt action 223 and AR-15 loading. You'll almost never go wrong using Sierra's load data. What shoots well in one gun doesn't always work out in the next, therefore; you are going to have to experiment with your weapon to find the "perfect" load. Remember, regardless of what some "experts" have put out in the past, if you're weapons has a 1-8 twist tube, yes it will very likely fire 52 grain SMK's well, don't be afraid to try the lighter bullets, they very often can shoot like a house on fire! I've read on this very board, an "expert" chewing a guys ass off, because he wasn't shooting "At least 69gr bullet" with his 1-8! Don't get sucked into this type of nonsense, idiots like that are a dime a dozen. Good luck in your load development, A couple of powders that haven't been mentioned, that I've had great luck with are N133 and N135.