dude, don't walk away from ATN....RUN!
I bought one about a year ago for backyard plinking with the AR15. It lasted a whopping 300 rounds before it stopped working. Every shot, the dot blinked off. A sharp smack to the sight housing would bring it back. EVERY SHOT. I emailed the place I bought it from to get the warranty info. I received a web address that no longer worked. I did some detective work and found a working number/web address...I haven't been able to get anyone to pick up the phone, and haven't received a response to repeated emails. Do yourself a favor and save up for something decent that has a customer service dept located somewhere in the USA. Aimpoint, EOTech, Leupold, WHATEVER YOU LIKE. Please, please, please PLEASE don't waste your money on this POS!
BTW, I wound up fixing it myself. I took it apart and found a loose contact that needed to be built up a bit (no big deal voiding a warranty that I couldn't get anyone to honor) I then moved the ATN over to the 10/22. It lasted almost 500 rds on the 22 before it broke again...different contact broke off. Now running EOTechs on the AR15, DPMS308 and a Bushnell HoloSight on the 10/22 and no problems to date.