content: Typical AR mags are 30 rounds, many folks will own a 20 round or lower mag just because they are cheap and small,  but I've seen AR mags that go up to 150 rounds Big ones are more expensive so I'm betting he either had one drum or a few spares, but in tight night club if I had green tips I could shoot well over 100 people with 30 rounds so I'm betting the guy had 2-4 mags depending on his ammo.