I am preparing to buy my first AR. Will be using it on coyotes and some neighbor's pesky dogs who insist on chasing my cows, then standing off 300 or 400 yards making obscene gestures. I need something economical to shoot and won't scare the pants off my wife when she shoots it. I've been doing a lot of reading and think that a Bushmaster flat-top, 20", topped with a 6x20 Leupold that I already have. Am I on the right tree? Any suggestions would be welcome. Thanks....