Google usually helps but coming from the military we are trained with the m16-m4 same thing just with a burst fire option but , the AR 15 is an air cooled , shoulder fired gas operated Simi automatic rifle that accepts a 30 round mag ... Accurate up to 500yards I had held tight groups at 300yards , they fire a 5.56-45 round or the .223 , an AR 10 is the same thing but fires the 7.62-51, or the .308...