I have a Bushmaster AR15 with a 24" DPMS bull barrel and I'm shopping for some optics. I'd like something "tactical" in flavor, but would like to keep the price under $500. Most shooting will be done at cute, furry little animals anywhere from 100 - 300 yards and so a max magnification of 20 to 24x is preferable. Any advice or suggestions would be appreciated. Thanks.