moot1337

It all really depends on what parts/dimensions you use when making the spud gun... Basically, when it comes to about standard size spud guns (ranging from 1" to 3" barrels or length from about 4' to 8') I find there to be about four classes:

1) Large combustion chamber directly connected/reduced to a smaller diameter barrel - These are about the cheapest to make, and have about the smallest range and projectile choice. They're a good type to try when it's your first time building one.

2) Large pressure chamber directly reduced to barrel size, using a manual ball valve and air pressure from bike pump or air compressor. These offer a bit more functionality and power while sacrificing mobility...with higher pressures the projectile(s) will shoot much farther, so it is usually best to have a compressor rather than a bike pump when using these.

3) Large combustion chamber with a choke - at the end of the combustion chamber, a choke reduces the diameter to 1-1.5" (usually) and then widens to a larger diameter pipe than the choke for the barrel. These guns are much more powerful than standard combustion guns, and when built properly they are usually more powerful than the ball valve pneumatics. Another plus is that you can fire larger projectiles, but they are a bit more expensive to build due to a bit more fittings.

4) Large pressure chamber using an electronic solenoid to release air into a barrel which can either be as small as the valve's fittings, or up to 3-4" - these along with the choked guns are about the most powerful.... pneumatics being a bit more expensive. They are also the most versatile - you can even load them with water to have a large portable splash. The downside is reduced mobility and cost... though they can use a bike pump, an air compressor is definately more desirable, and sometimes the solenoid valves and batteries to power them can get fairly expensive.



There are probably a bit more designs than this... these are the ones I've personally dealt with, though.