if you have a zip gun its quite hard to get bullets isnt it? (if your underage) i thought about this and i came up with 3 aliteniteves
1. go too a construction site and look through the skip if you find a red plastic strip with 10 empty shells a little smaller than 22s look for more red strips some times there are unfired shells on the red strips. you get about 10 unfired bullets at least with 5 strips.
2.go too a hardware store and buy the red strips mentioned above.
3.make your own bullets!
just get some alluminium tubing and toy gun caps and black powder (see my formum topic on lock bombs)insert one of the caps into the back off the allo pipe the diamiter off a 22 put glue to hold the cap there and put 40 miligrams of black powder in than a screw or lead or something as a warhead.