Introduction:
In the past, many people have experimented with the power generated by the conversion of dry ice into gaseous carbon dioxide. The most common use that I have seen is the dry ice bomb. The dry ice bomb is easily made by using a two liter plastic bottle, some hot water and some crushed dry ice. To make one, one simply puts about a cup and a half of crushed dry ice into the bottle, adds hot water, caps the bottle and throws it. These bombs are not a joke, and have been known to blow a metal trash can fifteen feet into the air, as well as bursting the bottom of the can. If you make a dry ice bomb, you had best throw it before it explodes due to the enormous force generated by the explosion of the bottle. A friend of mine waited a bit too long on throwing one, and he jammed three of his fingers badly, got a huge bruise on his left leg, and one of the plasic fragments was propelled with enough force to puncture his tennis shoes and cut his foot all to hell. In short, be careful with these things.

One day in May of 1985, an idea was introduced to me by a friend. His plan was to control the force of the expanding dry ice and harness it to a useful end. The result was the dry ice gun. In following these plans, please keep in mind that when dry ice is finished expanding, it can generate pressures of up to 2400 PSI...for this reason, I recommend that when arming the gun and when disarming it, you hold all valves OPEN, and that you wear a pair of protective goggles at all times. I will take no responsibility for injury that occurs because of the content of this file, or through the use of this information. This information is intended for educational purposes ONLY.

Materials needed:
The materials required will vary for each gun produced because of the nature of the construction itself and the effect produced by using different parts. The following parts, however, are necessary for a gun with moderate power and range:

1- Standard valve. I recommend the kind that is just a lever and turns 1/4 turn to open or close and has 3/4" connectors.

1- Blow gun (These can be found at auto parts stores... shop around a little and get one with the highest pressure rating you can find (probably 150 PSI)). This will be sometimes referred to as a valve also.

1- Length of hot water PVC piping...this will be used for the barrel. I recommend that you use 3/4" piping, because that is the kind that fits paint pellets of the type used in KILLER best. Note, however, that it is possible to launch anything up to the size of an egg with pleasing results, provided that the barrel is large enough in diameter.

You will also need various lengths of regular lead or steel piping (to construct the actual gun), and adapters to get the blow gun to fit the rest of the gun (blow guns usually have connectors that are 1/4" in diameter, while the rest of the gun (except the dry ice container) should be constructed with 3/4" fittings). You will also need an end cap to go on the end of your dry ice container and probably an elbow joint.

Optional parts:
1- Standard valve (same kind as above, but with a shorter lever).
1- "T" joint with 3/4" connectors all around.
1- 6 or 7 inch length of 3/4" diameter pipe.
1- 3/4" end cap.
Form-a-gasket and pipe dope

Construction:
Because of the nature of the gun, step-by-step plans are not possible. However, a diagram of the gun will give you an idea of what has to be done, and construction tips should prove enough to allow successful completion of the project.

Diagram:
trigger (part of the blow gun) standard
adaptor______________ : valve
\ : \
: : :
______________________ : _ ; _____:______
! !\__ __!___/! ! \
! barrel ! __!__!__! ! O ! \
!______________________!/ / : : \!___I__!__ \
joint B____________/ : : : I \ \
blow gun_____________/ : : I / \ \
pressure chamber________/ : I / !_____!<-joint A
adaptor____________________/ / ! !
elbow joint________________________/ /! !
dry ice container_____________________/ ! @ !
end cap_______________________________ _!_____!_
\!! !!
+-------+

Notes:
1- The dry ice container can be any size...the one I use is about 6 inches long by 2 inches in diameter. The larger the chamber is, the more shots the gun will fire before reloading is necessary.

2- The elbow joint can be left out...it will only make the gun in the shape of a straight rod rather than a "traditional" gun shape.

3- The barrel length can be any length you like, but very long ones are cumbersome and very short ones don't allow much accuracy. I recommend a length of about 2 1/2 to 3 feet.

4- all joints except the two marked 'A' and 'B' should be tightened as much as possible and sealed by coating the threads with the form-a-gasket and then putting the two pieces together and tightening them as much as possible. If you like, you can also caulk around the finished and tightened joint.

5- The joint marked 'B' should be tight, but DO NOT SEAL IT unless you do not intend to ever use more than one kind of barrel.

6- The joint marked 'A' should not be sealed with form-a- gasket like the others because it is the one that you will be filling the dry ice into the gun through. To fill the gun with dry ice, detach the dry ice chamber pipe from the elbow joint. Load the container with as much crushed dry ice as it will hold. Then, coat the threads of one of the pieces of the joint with pipe dope. This will prevent leakage of the carbon dioxide after it has changed into gaseous form.

7- The pressure chamber should be about 1 1/2 inches in length for a fairly powerful gun. The longer the pressure chamber is, the more powerful the gun. On a gun with a three inch pressure chamber, we shot a AA battery 500 (yes, hundred) feet across a parking lot. Such high power, however, is dangerous, and is not recommended for use in games such as Killer, but rather for target practice (on INANIMATE objects).

How to operate the dry ice gun:
Once you have the dry ice gun built and loaded, the first thing you must do is to open the standard valve and immerse the gun in water. This is to check for leaks. If any leaks are present, they will show up as streams of bubbles rising from the gun. If any are found, tighten the offending joint and put the gun back in the water. When all leaks are gone (if necessary, take the whole thing apart and rebuild it from scratch to eliminate leaks, especially on either end of the pressure chamber), release the pressure built up so far by closing the standard valve and then operating the trigger. You should hear a 'woosh' sound, and tie gun should kick slightly. This indicates that all is working properly. When loading the dry ice gun, it is important to keep both valves OPEN until the dry ice container is secure, and then close both valves. Even after you are sure that the gun has no leaks anywhere, it is good to immerse the dry ice container (while it is attached to the gun) in water. This warms the dry ice and causes it to change into gaseous carbon dioxide.

After the dry ice container has been immersed for 5 minutes or so, remove the gun from the water and dry it off. The gun is now ready to be fired.

Firing the dry ice gun:
This is the simplest step of all. To fire the gun simply place the projectile (I recommend paint pellets) in the barrel of the gun, open the standard valve for about a second and then close it. You should hear a muffled rush of air as some of the gaseous CO2 is bled into the pressure chamber. Aim the gun at who/whatever you wish to hit, and squeeze the trigger. For more power, you can leave the standard valve open and squeeze the trigger.

Disarming the dry ice gun