How To Make a Marshmallow Blow Gun
This is a project that's perfect for Scouts: it involves shooting something (marshmallows), it's very easy and cheap to make, and it really works well. You'll need about 25 inches of Schedule 40 PVC pipe, which is inexpensive and readily available from any home improvement store. The Schedule 40 PVC has an inner diameter of approximately 1/2 inch, which is a perfect fit for the mini marshmallows. You can cut the pieces of PVC using a hacksaw, or you can pick up an inexpensive pipe cutting tool from the same store that sells the PVC. If your Scouts will be completing the project themselves, the pipe cutter is a much safer way to cut the pieces.
Following is a list of the parts you'll need:
Layout the pieces as shown, and assemble them by pushing them together. It's best not to use any adhesive. Friction fitting allows for later re-configuration and cleaning, and makes a more-than-adequate seal.
One you've assembled the PVC, you're ready for a test firing. The mini marshmallows are loaded through the mouth piece, not the barrel. (Yes, the marshmallow does successfully navigate the two 90 degree turns without a problem.) Place the marshmallow just inside the mouth piece, place your mouth over the pipe, and blow hard. You should be rewarded with a very satisfying "thunk" as your marshmallow flies out of the barrel and hits whatever you're aiming at. Hold the gun using the two pipes extending down from the main barrel.
When using the marshmallow blow gun, be aware that the area you are shooting in will soon be covered in sticky marshmallows, so pick your location carefully. Its best to do it outside. Try not to get too much saliva in the mouthpiece, as the marshmallows will start to stick and create a messy blockage. If this does happen, just take the gun apart and clean it out. So far, every Scout I've observed using a marshmallow gun has decided to try loading multiple marshmallows into the gun. This works, but not as well as firing only one. Feel free to disassemble the gun and put it back together in different configurations. My Scouts have discovered a number of different workable variations. You could also paint the guns with a camouflage theme, or anything else you can imagine.