The spud gun design is just an example. The principle of the design is a gun that can only launch one paintball at a time, like a musket. Guns that fire multiple charges of paintballs are not allowed! However loading several paintballs in the barrel and then firing is allowed as it acts like scattershot. The loading of the gun can be from the muzzle or the breach. Compressed air is a valid propellant if you can get it to work better than I did. The core of the game is to have to be careful with your shots. Instead of spraying the forest with paintballs and running, the name of the game here is careful aim.
You must wear all the safety gear you would normally during paintball. Despite the blow out cap, the paintballs can deliver a painful welt. Make sure to wear a face shield and any other protective gear.
With the variable strength of the guns, it is important to not try to hit the other players harder than is necessary to burst the paintball. Any player that causes a wound by breaking skin is disqualified.