Started my son with my AR 223 as well. I'm using Barnes 55 gr I think and it groups well. I went with 10 rd PMAGS... they sit almost flush when inserted. The 30 rd mags catch everything in the deer stand when moving it around while trying to position. Never had a lick of trouble with the PMAGS yet. I'm fixing to move him over to a 25-06 so hopefully the AR was good training.