5 Mags unloaded if not more. 20rds works well if State law allows You will be making mag changes, and shooting strings of 13 rounds or more in a row. We HIGHLY SUGGEST you bring 5 mags (or even more) to your Appleseed Shoot. Now if you only have one, or two, don't feel you can not attend if you can not get more before the shoot. If you can shoot 10 rounds, you can participate at Appleseed (even if you can't, we still want you there and you will still learn a ton). Two mags should be an absolute minimum, so try to have at least two.