Hi, my name's Justin, and this is my first instructable. I was working on this project before I noticed this contest, and then when I saw it, I was like, ok, I'm totaly entering! Well, anyway here it is.

What I like about this project is that it's pretty simple and cheap, yet it delivers a heck of alot of fun! At leastI think it does.

Step 1: Tools,

Here is a list of the tools and materials needed for this project.

Tools:
             a couple wrenches,
             PVC glue, (optional)
             Knife
             air compressor,,, if you count that as a tool.

materials:
                   Fire extinguisher,
                   Hose,
                   PVC pipe
                   PVC and Brass connector things.

Step 2: Hardwear Store.

So your going to have to go the the local hardware store to get some stuf. I'm pretty sure the total amount of money I spent to get it all, only came to around 6 bucks, not including the fire extinguisher,,, wich we had just laying around the house.

So your going to need:

3/8" Comp. x 1/2" MIP w/Insert:
this certain Hose, I dont know exactly what its called, but I took a picture:
a 1/2 inch to 3/4 inch PVC conection, with the inside of the small end threaded:
and a 3/4 inch PVC pipe, of whatever length you feel like.

ya, I took a picture of all of this stuff, so you can see what it looks like.

Step 3:

Unfortunately I have recently lost the black hose that comes on every fire extinguisher, so I can't take a pickture to show you, but its the hose that ataches to the threaded part of the fire extinguisher in the picture.

This black hose is NECESSARY for represurising your fire extinguisher with air. If you dont lose it, it will save you "Time" "Work" and "Money"

Step 4:

The black hose that came on my fire extinguisher, had a hard black nosil thing at the end. This needs to be cut off with the Knife, leaving as much hose left as posible.

Now go to your compressor. It is likely that it still has the attachment for pumping up tires. Well your going to want to change that tire atachment, for a __________.
The pictures below will show you how to do this.

Step 5:

Now that you have that wierd attachment on your air compressor, instead of your tire attachment, you need to slip the ring thing, thats in the picture,,, OVER the end of the black hose, that you cut the plastic thing off of. You know, the one that came with the fire extinguisher.

Step 6:

After you have the ring thing on the cut end of the black hose, slide the cut end of the hose, onto the "THING" on the end of the air compresers hose.

After the hose is slid onto the "THING" as far as you can get it, tighten the RING with a screw driver.

Sorry guys that I lost that one hose, so I couldn't take a pic of it to show you better.

Step 7:

Now, we're getting close to done. =D

I'm going to show you how to asemble the Barrel of this air gun thing, to the actual extinguisher. Try to folow the pictures below.

Step 8:

Well, were you able to follow the pictures ok?
Now unattach the silver hose from the fire extinguisher,,
Take your extinguisher outside and let it all go like you were actualy trying to extinguish a fire. The reason you're doing this is to let all of the powder out. You need to represurize and blow it out again many times, before the powder finaly stops coming out. Heres a tip, you might want to blow it facing down wind during this step, because that powder,,, doesn't really taste all that great. =P

Step 9:

In the last step, I told you to get all the powder out, and I said you would have to refill it with air a couple times before you were done. Now I'll tell you how to refill it with air.
It's pretty simple,,, just take the hose atached to the air compressor, and screw it onto your fire extinguisher, then, while (HOLDING DOWN THE RELEAS VALVE ON THE EXTINGUISHER) turn your air compressor on. Its verry important that you hold down the realeas valve the whole time your air compressor is running, otherwise you might split a hose or something. Ohh, and incase you didnt know,,, the "Realeas Valve," is just the "Trigger thing," that you pull to actually make the fire extinguisher let the air out. or,,, in this step,,, IN.
When you feel the pressure in the extinguisher is high enough, try to turn of the compressor, and let go of the release valve, at the same time.

VERRY IMPORTANT!
On my fire extinguisher, theres a litlle pressure guage that tells you how many PSI is contained in the extinguisher at that moment. The green area on this little guage is the recomended PSI for normal use,,, and it should also have a WARNING mark after the green area,. I do NOT recomend trying to get the PSI close to the WARNING mark, unless you want it to blow up in your face,,,,, and you DIE!
I recomend keeping the PSI "SAFELY" withing the green mark, and everyone will stay happy.

Step 10:

After you have refilled your extinguisher a few times, and the powder has stopped coming out,,, then you my friend,,, ARE READY TO START HAVEING FUN! =D

Simply refill the extinguisher, then screw on the Barrel of your air gun,,, and stick something in it. =) see? easy.

Now,,, I have a really sucky conpressor, thats only made for 125 PSI, but its in such bad shape, I have trouble believing that it puts out even 100 PSI; but even that is PLENTY of PSI to have fun with!
You see the basketball in the pic below? Well I shot a NAIL at it my first day playing with the thing. Of course, I was using a different barrel size. The barrel size in this instructable, is much bigger then what I was using, so you can modify it if you want. Anyway,,, when I shot the nail at the basketball, at first, I thought I missed, because the basketball was just sitting there, not moving. So I walk up to it, and yep,,, I dont see any holes in it. But then I pick it up, and I can feel that the nail was INSIDE the baskeball.
It was pretty cool!
So anyway, this really isnt a toy. If your gonna let your kids play with it, I HIGHLY recommend never leaving them unsupervised. It might be a good idea to wear some safty glasses also.

Have Fun! And I hope I was able to get the instructions across pretty good, if you have any questions, just Message me.