Yeah, they do that. But surprisingly, they don't have to scavenge for fully automatic weapons. They're everywhere. Everybody has one. Normal people have to be very rich and connected to obtain a full auto these days, but after the zombies come, it appears that every Bubba and his brother had a handful of 'em! And not just the little personal ones either. Belt-fed .50BMGs mounted to the back of their pickups even.