Your open field and tree belong to someone and probably have public access. This means that in spite of your best efforts someone will inevitably be injured. You must be very young or daft not to consider the consequencies of firing your gun in any circumstances as described. At the very least, one day the tube will weaken, rupture and discharge its contents in your direction. Brass: Often brass fittings are used on spud guns for small parts of the construction like fuel systems, because it is one of the most common materials for small pipe fittings. Occasionally large parts of spud guns are machined entirely out of brass. [14] The ATF has previously examined potato guns or spud guns as devices using potatoes as projectiles and used solely for recreational purposes, do not meet the criteria of a destructive device defined by the National Firearms Act, or the Gun Control Act. They have however classified said guns as destructive devices when they used incendiary tennis balls. An extremely high-velocity potato cannon is featured as a project from Nelson "Big Head" Bighetti in Silicon Valley (season 2). Barker-Griffith, Ann E.; Streeten, Barbara W.; Abraham, Jerrold L.; Schaefer, Daniel P.; Norton, Sylvia W. (1 March 1998). "Potato gun ocular injury". Ophthalmology. 105 (3): 535–538. doi: 10.1016/S0161-6420(98)93039-1. PMID 9499787 . Retrieved 15 August 2011.

Compression Fittings: primarily seen on copper pipe spudguns, the compression fitting squeezes a metal ring against the pipe between a nut and the fitting body to form the connection. Easier than solder fittings and requiring only a spanner they are much more expensive and are of greater weight. According to the NFA and GCA previously mentioned, it must be muzzle loaded, not rifled, or use any projectile which is intended to be used as a weapon. Any device using compressed air would be completely exempt from both. Metal welding: used to form strong joints between similar metals by melting the points of connection together. It is an uncommon process in spudgun construction due to the equipment necessary to make the welds. A dry ice cannon uses the sublimation of solid carbon dioxide to generate the gas pressure to propel a projectile and is a variation of the burst disk cannon. Any pneumatic with a potential power output exceeding 12 ft-lbs will also fit within either section 1 or section 5 (Section 2 cannot be air powered)any device capable of propelling a projectile with a muzzel energy greater than 12 foot pounds is classed as a firearm ( so most spring air rifles are not a firearm ) Steel: The very high-pressure rating of steel piping makes it a familiar sight on high-powered hybrid cannons. It is however much more expensive than any other common piping material. The extra weight and joining difficulties are also a consideration.

Heating the gases to far higher temperatures, and thus giving them more energy. This allows hybrids and combustions to achieve supersonic velocities. Special effects cannons: In film and theatre productions, pneumatic cannons (such as an air mortar) are often used as a pyrotechnic-free method of material projection. These can vary from simple ball valve, manually operated models to electronically triggered designs operated from a remote control panel depending on the exact requirements. This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. ( September 2020) ( Learn how and when to remove this template message) By the combustion of a gaseous fuel-air mixture; this is generally called a combustion launcher, and its pressure is limited primarily by the energy density of the fuel-air mixture (less than 100 psi (0.7 MPa) with all safe fuels). Pierson, Hazel M.; Price, Douglas M. (Spring 2005). "The Potato Cannon: Determination of Combustion Principles for Engineering Freshmen" (PDF). Chemical Engineering Education. 39 (2): 156–159 . Retrieved 15 August 2011. [ permanent dead link]Ball Valve: Made out of either plastic or metal, ball valves are considered inferior by many enthusiasts due to their slow opening times. For those on a tight budget or in low-power setups, ball valves are ideal. Some choose to modify their valves by attaching a pneumatic actuator or spring to achieve a faster opening speed. Alternate designs have also been used which use a sharp projectile to puncture the burst disk, like a mortar [16] or using a manual puncturing device to trigger failure of the disk. [17] These allow total control over burst disk cannons without the need for hybrid technology and materials as simple as plastic tape can be used for the disk. Burst disk cannons have also been made which are fired electrically, using a nichrome wire to trigger failure by heating. [18] Connections [ edit ] Welding, soldering and gluing [ edit ] It comes down to what you're doing with it and who you are. A young teen responsibly using a combustion spudgun will probably get talked down and the spudgun taken away. Pneumatic spud guns are classed as air guns in New Zealand, which means the owner must be either over 18, or over 16 with a A-Category Arms License. Combustion cannons are deemed a firearm, requiring the owner to hold an A-Category License. These laws are rarely, if ever applied and spud gun ownership and building has proved a popular hobby with many New Zealanders.

Golf ball launchers: at some charity outings players can make a donation and launch a golf ball over 300 yards and use that as their tee shot. Usually the vendor hired by the event organizer launches the ball for safety and liability reasons. In the TV series House, M.D. episode " The Dig", House is attending a spud gun show with Thirteen, where he uses the spud gun to threaten a teenage competitor who taunts House. A MythBusters episode tested a potato cannon held together by duct tape compared to one held together using PVC bonding agent. Another episode, testing MacGyver myths, supplied Adam and Jamie with the materials to build a potato cannon as part of a challenge to "MacGyver" up a way to signal a rescue helicopter; however, they used the piping and other supplies present to build a large kite instead.A hybrid using a fuel and air mix at twice atmospheric pressure is said to be using a 2X mix. Higher mixtures can be used and will produce even higher pressures. The fuel and air need to be measured and matched carefully to ensure reliable operation; hence the use of accurate air pressure gauges and fuel meters. A spud gun is not considered a firearm unless it fires a projectile faster than 152.4meters per second and at a muzzle energy exceeding 5.7 Joules based on the definition of a firearm in the Canadian Criminal Code. [2] A spud gun may be interpreted as an imitation firearm, and therefore it would be illegal to have it in possession in a public place. The spud gun would most likely be considered a dangerous weapon, and therefore if an offense is committed with it, a possession of a dangerous weapon charge could be issued.