I'm getting ready to build my first AR, and I'm looking at a red dot with a 3x magnifier. My build is a 20 inch with RRA 2 stage trigger, and is intended to be used for some distance shooting, but it would be fun to have the <100yd options open. I figure I can use the red dot for close range practice, and keep a 3x magnifier on a quick release mount or one of those nifty flip-to-the-side deals, and get the best of both worlds. I may find it better to put a longer range scope on, and use irons when I'm feeling too lazy to set targets 200yds out. If anyone here has used the dot+magnifier setup, how much distance can I really expect to get out of it? Would it be practical at, say 300yds?