I mostly use quality M193 and M855 in my ARs for both shooting and HD. A lot of guys like to use the heavier 75 gr stuff like TAP for defensive purposes. Look on the usual websites for mags. USGI 20 and 30 round, PMAGs, Troy mags, and Lancers are all fine mags. AIM surplus has the Troy mags right now at a good price. You picked a fine rifle for your first AR, have fun!