Not only marbles, but batteries, M&Ms, nails ...  all stuff that can take out a blue helmet if Carter's people get your 9mm.   The author began his journey of discovery after buying a cheap air compressor at a yard sale.  He tried to explode a 500 ml plastic soft drink bottle, but 100 PSI (the compressor's max) tweren't enough.  I happen to know that it takes 150 PSI to 'splode a Coke bottle (don't ask how I know).  Complete, illustrated instructions.  Hey, I'm starting to sound like an urban guerrilla. a right wing version of  H. Rap Brown.  "Don't trust anybody under 50!"   "Up against the wall Liberal MoFo!    Hoo-ahhhhh!!!!!!!