6mm plastic pellets, they weigh .12 .20 or .25 grams, very light, they hurt, like a mother, the guns are either spring, gas (propane) or electric, the shoot anywhere from 250 to 500 fps
imagine paintball with real weapons, full auto and huge magazine capacity, further range etc
drawbacks: not as easy to see for sure when someone is hit, people can cheat
solution: light em up so bad they have to scream