Well, I have been doing lots of research about making a snow gun and have been talking to lots of people. Anyways, there is only 1 real important thing to building snow...
an air compressor.
You will need an air compressor that put's out at least 4 SCFM (CFM) @ 90 psi. Once you get this compressor, the only other things you need are a garden hose (water source) and cold temps! Basically that's it! It's very simple. I am awaiting the arrival of my air compressor.. I ordered it online last week, so it should be here this week. Then i will be able to test it! I'll put up some pictures of my snowgun that i built probably tomorrow..
-Jason