Potato guns are, as per the name, inherently guns themselves. Although they may be made from PVC, and metal, they still harbor the ability to cause severe harm, or even death if used improperly. Proper care must be taken to insure that potato guns are handled properly to help prevent injury to yourself, & to others around you.    No matter if you build and use a combustion gun, or a pneumatic gun, they still contain the ability to propel projectiles at extremely high speeds. One person has build a marble gun, that runs of pneumatics and can propel marbles at speeds in excess of XXX Hundred fps. That's right around 2/3 the speed of a .22 cailber bullet. However a marble contains anywhere from 3 to 5 times the mass of a .22 bullet, AND it's made of glass instead of lead. There are others Dan Thames that have built pnuematic cannon that can shoot soup cans of concrete nearly all the way through a house. No matter the potato gun that you build, you MUST keep in mind that what you have, despite it's outward appearances is actually a Gun, a weapon, and you must treat it with the respect that they command.    There are a few basic, and obvious rules of handling and use that apply to potato guns. You should treat them just as you would a firearm. In case you have no clue as how to properly handle a firearm, I'll list a few of the basic lines of etiquette & handling: Do NOT point them at people, animals, cars. or buildings. Do NOT shoot at people, animals, buildings or anything else you don't want to shoot. Always treat the gun as if it were loaded, nevermind what state it actually is in. Don't leave the gun out where small children can get ahold of them. Don't put the gun away loaded. Don't shoot over roadways, or within 50 feet of roadways. Inspect the gun for stress cracks or loose fittings BEFORE and AFTER every firing.    Now I understand that with most potato guns you have to actively do something to prepare them for firing, whether it be the injection of fuel (propane/hairspray), or the pressurization of the air chamber. And that thus requiring such, they for the most part will not be able to readily fire if a small child, or other unknowing person were to come along and pull the trigger. Another thing is putting them away loaded. Although it may seem kinda pointless, I have loaded the barrel on my combustion gun, and then put it away. I didn't notice it was loaded till the next time I went to shoot it. Rotten potatoes stink, smell, and are REALLY nasty & slimy to clean up. So if even just for not wanting to clean up the mess, don't put them away loaded.    The bottom line comes down to this: Treat the potato cannon as you would a loaded and ready to fire gun. Don't point it at anything that you do not want to shoot & destroy/harm. Although they may seem like toys, they still have the ability to kill just like a firearm. Just use Common sense and try not to become a statistic, or get arrested while having fun.    Up Next.. Various Uses >.