SpudFiles

hi, i am making a pnuematic "sniper" cannon and i was wondering what barrel length to use. the barrel is going to be 1" ABS pipe and it can't be too long.

well as they say longer is better to make it practical I'd say about 50-60 cm.
(you might need a bipod or monopod )

Redcoat wrote:well as they say longer is better to make it practical I'd say about 50-60 cm.
(you might need a bipod or monopod )

how much does the barrel length affect the muzzle velocity (longer barrel = higher velocity, correct me if i'm wrong)

quite a bit i'd say judging from the mythbusters episode where they made a cannon with a 50ft barrel or even look here.
Killjoy also used a 50ft barrel.

Happy SPuddin'

that is one massive barreled cannon, i don't think mine will be quite that long lol.

Longer barrel usually does = more velocity, especially if you have a slow-ish opening valve(ball valve) or a low flow valve(sprinkler).

A longer barrel lets the projectile get pushed out by more air pressure, then if you had a shorter barrel where the projectile would leave sooner and before all the pressure is used to help launch it.

What type of valve are you using? Whats your chamber volume and what are you shooting at what pressure?

You should download GGDT, don't ask just google it. It lets you play around with figures to find the optimum barrel length(and more) for the most power possible from your cannon.

The longer barrel, the better
(and more accurate)

Saboo wrote:The longer barrel, the better
(and more accurate)

In most cases yes, but you can't have an infinite barrel length, you need to find a barrel length that is practical and effective for your use, like if you want it portable-ish, yet powerful 1.2m is usually a good bet, but if you're trying to get supersonic on a hybrid you can go up to 10m.