LOL, he's right. Nothing fancy going on here. Basically, the pin holds the thing together. When you pull it out (Which produces a nice grenade pin pulling sound
)basically, all you're doing is holding it together with your hand. The spring is really, really strong, so you just hold the thing pretty damn hard until you throw it. By the time it hits the ground, the spring pushes the two halves apart and the BBs fly everywhere.