Simple, relatively reliable, cheap as dirt miniature spud gun

Parts :
1. Lighter Igniter (Peizo Electric Igniter)
2. Bic Pen
3. Crayola Marker
4. 1/2 in. Screw
5. Generic Hairspray
6. 3 - 5 in. of small wire

Tools :
1. A punch that can make
a hole slightly smaller
than the diameter than
the wire from the igniter
(a thumb tack followed
by a small nail)

Step 1: Preperation

1. Remove the tip of your Bic pen by biting and pulling or using pliers.

2. Remove end cap ( Be creative, theres no best way, I just cut it off, but make it a clean cut! )

Barrel Is Complete, Set Aside.

3. Remove the felt tip of the Crayola marker ( Messy, dispose of wisely )

4. Punch small hole in the rear of the marker and insert the screw. This will serve as a 'handle' to remove the end cap.

5. Pull, thus removing the end cap of the marker. Do not discard, you will need it.

6. Remove the ink tube inside the marker ( Again, be creative, tweezers, etc., discard of wisely )

7. Poke two small holes 1mm in diameter about 3/4in. from the rear of the marker at the 12 and 6 o'clock.

The Chamber Is Complete, Set Aside.

8. The peizo electric igniter probably is still inside your BBQ Lighter, so we're going to need to remove it with the wires intact.

9. Usually the igniter comes with one wire and a contact pad, if so find another wire about the same thickness and attach to the contact pad. ( Once again, be creative )

10. Strip the ends of the wires leaving about a millimeter of exposed wire.

Step 2: Assemble

1. Insert the wires in the two holes you made in the chamber ( marker ) and take a peek inside the chamber and make sure every time you press on the igniter you see a spark jump from wire to wire.

2. Take some precaution and shield yourself from the shock of the igniter by wrapping it with electrical tape or find a small rubber end cap by coincidence and place on contact pad over the wire. Doing so will give you better results upon ignition.

3. Insert barrel ( Bic pen ) into where the felt tip of the marker used to be and you should find that it fits snugly ( Glue if you wish, I decided not to so i can breech load it instead of ramming the projectile down the tube )

The Miniature Spud Gun Is Complete, Make Projectiles... Be Creative Damnit !

Step 3: The Silencer

Pretty much the same base parts of the spud gun itself, a cheap Bic pen and a washable Crayola marker. Take out all of the insides of both, discard the whole tip of the pen, the ink tube, and the end plug of the pen then remove the tip of the marker and the insides by popping out the end plug (without destroying it) and removing the ink sponge/tube/cartridge by the means of pounding the open end of the marker on the table or tweezers using common sense to guide you.

Take the Crayola marker and ream the insides mostly the part where the tip was so it can fit the Bic pen through

Make another hole big enough in the end plug (not the cap), in the center to fit the pen all the way through

Take the hollow pen tube and using an exacto blade or a sharp point razor blade, make a series of tiny counter-sunk holes (not depicted, too lazy to post new pics) about 3-4mm in diameter down the sides of the pen tube leaving about 1 1/2 inches of clear (no hole) material at the end of the bore and at the tip of the muzzle.

Make sure there is no debris or burrs on the inside of the barrel and that the barrel didnt warp from cutting or anything else.

Push (pound, an airtight fit is best) the pen tube into the marker about 1cm passed (further inside) the rim where the marker tip used to be, this makes it so you can attach the silencer to the barrel of the mini spud gun.

Replace (pound) the end plug (again, not the cap) back into the marker making sure the pen tube goes through the hole in the end plug, that the pen tube is still recessed 1cm below the rim at the tip, and that you didnt mar the muzzle of the silencer.

There will be about a cm (idk, I dont remember) of the pen tube protruding from the face of the silencer, remove it if you wish but take special caution not to ruin the muzzle and that you dont leave burrs on the inside of the barrel as it may hinder the already ghetto enough spud guns performance.

Affix the silencers end with the neck onto the muzzle of your miniature spud gun, make sure that the main and silencer barrels are flush against each other or to be fancy, put a rubber gasket between the inside rim of the pen tube and the muzzle of the barrel attached to the chamber with the inside diameter smaller than the bore and ghettolectric tape the silencer to the barrel attached to the chamber and check once more for a flush fit for a more permanent silencer. I usually shorten the main barrel between the silencer and the chamber so that the propellant would have enough room to push the projectile out of the barrel and the silencer.

It still hurts according to the decibels and multitudes of profanity in the general area and the velocity of various hand held objects being thrown back my general direction after firing rather well placed shot in my little sisters abdomen. It doesnt really make the spud gun quieter. Although, in some test/curiosity/boredom fires the only things heard from the spud gun was the piezolectric igniters striker being hammered onto the unseen inside surface while hearing the wire spark and the sound of a either a shriek or a projectile hitting a surface confirming that the projectile has in fact left the silencer and that the projectile gains a reasonable to slightly peculiar, higher or lower amounts of distance to hit its intended target or any other object in your general direction. It kinda alters the sound created by firing the spud gun in a weird, trippy way.

Try putting an ever so slight choke in the end of the main muzzle bore, the tube attached directly to the chamber, choke the business end of the main barrel as if the silencer wasnt there somehow, the projectile requires more pressure to escape the barrel because the choke slightly obstructs until a certain pressure is reached, this makes the expanding gas from the propellant build up in the barrel and if the alteration is done correctly the extra pressure will force the projectile out of the muzzle at a higher velocity. This requires X or lower (x= how much expanding gas it takes to fill the barrel and a little excess just for good measure) volume in milliliters not decibels inside the barrel and in any cavities the gas may take up inert space such as the cavity between the inside walls of the marker and the surface of the pen tube inside of the silencer you are in the process/decision/satisfaction-of-completion of making. If theres too much volume the gas expands and diffuses in the inert space in the barrel and silencer so you end up with a squib round (a projectile that has failed to leave the barrel) or poor velocity resulting in a weak shot. The preferred amount of volume is determined by the size of the chamber and how much the propellant expands after ignition. Lets say Assy.A has a big chamber with a weak propellant has moderate to poor performance and Assy.B has a strong propellant in a small chamber, Assy.B could have the same or more likely more velocity than Assy.A. The overall quality and performance of this spud gun relies on the kind of junk you have around and the kind of toys you own.

Step 4: Fire

Load the projectile into the breech of the gun and reinsert the barrel. Spray a very small amount of hairspray into the chamber. You will almost always spray too much in the chamber so to fix this blow lightly into the chamber, it takes practice to get the right fuel or hairspray : air ratio correct. Close the chamber with the end cap immediately and fire at will.

Step 5: Projectiles

This mini cannon can basically shoot anything that can fit in the barrel so here are a few ideas on ammunition:

1. Paper cone. ( depicted in step 1 )

2. Those little popper things you give to your kids on the 4th of July.

3. Cigarette filters.

4. Cut a 1/2 in. slice of a potato and take the barrel and press into it making a nice mini tater slug.

5. Pills.

6. Q Tips. {TheMattHatter}

7. Technic/Knex Rods. {Trans_Am}

8. Eraser with Needle in it... Ouch. {Girrrrrrr2}

9. Straw with bb jammed in the end wrapped lightly in electrical or magic tape.

I'm open to suggestions feel free to comment and add more ideas and I'll put them here.

Step 6: Ok So I Got Carried Away

Yeah so I was really high last night so I just went nuts on the gun, Changed everything. Now its on steroids, I made it look like (or tried to) the AK - 47 Gas-Operated. It features a few moving parts such as the rear part of the upper receiver and Ive also built a working silencer for it for that stealth touch.

Step 7: Why Doesnt My Spud Gun Fire?

For the ones who simply dont have the effort to spare looking at problems users often experience while making, operating, or modifying the miniature spud gun and the intricate and detailed answers I provide with meticulous attention paid to a legible, understandable, and accurate solution or suggestion to all of the inquiries and enigmas Im intelligent enough to answer or at least the slightest of effort.

Problem:
You loaded a projectile that fit right, filled the chamber with a good propellant, sealed the chamber, and hit the igniter but the propellant doesnt ignite and nothing has exited the barrel but can see a spark leap across from one wire to the other when you squeeze the igniter:

Answer:
You put too much propellant in the chamber resulting in a fuel content too rich and dense to ignite by ghetto means. Depending on the propellant, chamber, and other small, meticulous variables the air fuel ratio has to be ideal to be able to ignite. Its hard to measure the propellant content by any reasonable means so the remedy given is not a sure-fire thing but with practice the process can be somewhat reliable. Spray a small amount of propellant in the chamber, use your reasoning abilities on determining how much is a small amount and if it fails experiment logically knowing that if you spray for X-milliseconds/amount-of-time (you dont need to keep track) and if it doesnt ignite, purge the chamber by blowing through the chamber (unloaded, no projectile) with a moderate amount of force until satisfied and sure enough that there is no gas in the chamber that can alter the series of trials and errors (unless youve found the divine method) and spray again with an amount a little less propellant and repeat until successful. Ive experienced the best performance by quickly pressing the spray button all the way down and immediately releasing it and then gently blow into the chamber. It takes a few tries until you get it right but its the best way I know how.

Step 8: Predator

New miniature spud gun.

Materials:
2 Crayola markers
3 Bic Round Stick pens
Candle lighter
3 Thumbtacks
Computer knob screw
Reticule from Vivitar Mini Digital Camera
Electrical tape