Building a spud gun: Tips / Tricks?

[Tayasaurus]

To my understanding of my local laws, that's illegal. However I think compressed air is okay where I live (still checking)

That and using a gas just seems way more dangerous than I'm willing to go for, considering it's only launching tennis balls, however someone else could take this to heart for their own project.

My friend did that thing with the flammable fuel spud gun and he scorched his eyebrows off. It was hilarious. I love being in the south.

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[Alyx Vance]

Me and a old friend of mine used to make firework mortars.. its all fun and games until it falls out of the barrel and into the floor of the treehouse.
And the stairs are gone

[LegendZ]

I have a combustion powered one, very similar to the one in the third photo, however, we used wood for the base so it's passable as an actual rifle. We use marbles as bullets to hunt for whatever's crawling around trying to eat off our farm.

[Axo-Tak]

Calculate and engineer based on the compressive stress involved when the potato is being fired. Otherwise, your gun will explode in your face. Almost no one wants mashed potatoes and shrapnel blasted onto their face.

[Racerboy]

shove one up your tailpipe

[XR-7]

Sorry for bad quality.  They saved at different sizes for some reason and the writing on the first one is tiny.  The first one is the air-powered one (turret is taken off).  The right side is where the air is pumped in and the green lever releases it, firing the potato.



The second one has a big screw-on valve on the back where hairspray is just sprayed in and the valve is put back on.  You pull a spark plug, igniting it, and it fires the potato.  Obviously the loudest, it sounds like a real cannon and sometimes flames will shoot out the end.

[AdinX]

Calculate and engineer based on the compressive stress involved when the potato is being fired. Otherwise, your gun will explode in your face. Almost no one wants mashed potatoes and shrapnel blasted onto their face.

Put that into simple terms
I'm assuming you mean figure out the pressure that would build up after firing?

[TheScout]

jesus christ, if you need a scope on a potato launcher it is a loving weapon at that point

[BlockoCrafter]

jesus christ, if you need a scope on a potato launcher it is a loving weapon at that point

Isn't it already pretty lethal?

[Tayasaurus]

jesus christ, if you need a scope on a potato launcher it is a loving weapon at that point

I don't think a scope equals lethality

[TheScout]

I don't think a scope equals lethality

if a rifle scope is necessary (unless it's for show), then it probably goes really, really far and fast

[Tayasaurus]

if a rifle scope is necessary (unless it's for show), then it probably goes really, really far and fast

An airsoft gun can make use of a high powered scope.

[Axo-Tak]

Rather than using a scope, why not make a special device that tells you the appropriate elevation to aim at?

A potato launcher's muzzle velocity might be too slow for a scope, so you might have to resort to this.

[Kirze]

Be a man and buy a real gun.

[AdinX]

Be a man and buy a real gun.

I'm 18 so legally I can acquire a rifle or shotgun
My mom is anti-gun
I have no job
I go to college in the fall
There is no way in hell my mom would ever pay for a gun for me

Unless you wanna buy me an M14 rifle, I'll stick to building a potato cannon.
Besides, like I said in the OP, I wanna mod it to fire tennis balls by giving it a 2.5~3" barrel



Question
If a tennis ball is ROUGHLY 2.5"
Should my barrel be 2.75" or will 3" be okay. I don't think they make 2.75" PVC but I can look.
I doubt 2.5" would work, sounds like the barrel would pop