okay, to try this you need to have a very strong gun... DO NOT try with a conventional pvc spudgun because it WILL blow up!! if you first fill your combustion chamber with pure oxygen you can use about 5 times as much fuel and thereby get a 5 times more powerfull explotion... this is because the fuel needs oxygen to burn and since normal air just have about 20% oxygen that limits the amount of fuel you can use... but by filling the chamber with 100% oxygen you can add mor fuel... the perfect fuel-air mixture with normal air is 96%air to 4%fuel. with the pure oxygen you can add 20% fuel... fore fuel you can try butane or propane, like the refill fore lighters... Once again i say that u need a steel spud gun if you are to try this!!
Play safe =)