Here's how to make a semi-reusable mold to cast cannonballs of almost any size and any metal, with mostly common stuff from around the house.
This is basically an idiot's guide, meaning it is quite long and detailed, but if you want to make your own super accurate and cool looking ammo, this is worth reading.
[Note to Schmanman: I demand that you make one of these for the SWAT gun
I'd send you one but lead is expensive to ship]
Here's what you need:
I shouldn't even need to tell you that gloves/glasses are important when working with molten metal.
1. Wax (any kind will do, as long as it isn't too hard and brittle)
2. A can to melt the wax in
3. Plaster of Paris
4. A Bowl to mix the plaster in
5. A piece of the pipe you want to make ammo for
6. Cardboard
7. Aluminum foil and rubber bands
8. Ducttape
9. Pam (any nonstick spay should work)
10. A knife, file, hacksaw, and pliers or channel locks
11. Charcoal/A gas grill, or really anything you can get to high enough temp to melt your metal.
12. A container to melt metal in (steel soup cans will work for lead, zinc and aluminum)
Here's what to do:
1. Take the foil and put it over one end of the pipe, and wrap rubber bands around it until it is sealed tight enough to cast wax in.
2. Spray the inside of the pipe down with Pam; this will make it easier to remove the wax.
3. Melt the wax in your can by putting the can in boiling water, and pour it into the pipe.
You will want the wax slug to be a little longer than the pipe is in diameter.
4. cut the wax into a rough sphere, make sure not to cut middle down any, as it will become a smaller diameter than your pipe. Soften the wax in warm water if necessary.
5. Take your rough sphere and roll it around on the end of your pipe. Allow the edge of the pipe to slowly shave off bits of wax until it wants to fall into the pipe. This may take some practice, but if you do it right you should end up with a nice, nearly perfect sphere. save your wax shavings, as you might need to use them later
6. make a cylinder of wax about 1/4 the diameter of your ball (no bigger than half an inch), and 1-2 inches long it doesn't have to look good, it will only be used to make a channel for the metal to be poured into.
Attach this cylinder to the ball by heating one end with a lighter until it drips, and then just stick it on and hold it in place while it cools.
7. Find a box, or get some cardboard and make it into a box at least a quarter inch bigger in all directions than your ball and cylinder (I found that a 4-stick butter box works good for a projectile 2 inches or less.)
8. Mix up plaster until it is about the consistency of pudding and fill the box a little less than half full.
Then spray the ball down with pam and lay it down into the plaster until it is EXACTLY half buried.
9. Now you need to make grooves in the wet plaster with your finger(see the pictures below), this will help the halves line up when you are ready to cast metal.
Let the plaster harden.
------------------------
------------------------
Now comes the point where you have to pour the other half of the mold. I've had problems in the past with the two halves sticking and cracking when they are taken apart, but have found a way to avoid this entirely. If you want you can skip the next few steps and go to 10, but I always do this to ensure I don't break the mold.
A. Take the plaster out of the box. rip it if you have to.
B. Get a frying pan or something fairly shallow and fill it with hot water. The water should too hot to touch, but not boiling.
C. Take thin pieces of wax (did you save your shavings?) and put them in the water. If you shine a light into the bowl you will be able to tell the wax is melting and forming a liquid film on the water. (picture shown below)
D. Make sure your wax ball still has pam on it. There should be NO pam on the plaster you poured.
E. Dip the ball-side of the mold into the hot water(its best to use kind of a rolling motion)
The side you dipped should have a paper thin coating of wax on it. The thin membrane of wax will peel off of the ball because it still has pam on it (this is a good thing)
F. tape cardboard to the sides of the mold to form a box to pour the other half of the plaster in. Spray the inside down again with pam and go to step 10.
-----------------------
-----------------------
10. mix the other half of the plaster the same as the first batch and pour it in, making sure that it is worked in to every small detail of the mold.
Let it harden overnight
11. You should now be able to separate the two halves relatively easily. If you have done everything right you might be able to remove the ball without damaging it so it can be reused.
DON'T PANIC if your mold has little air bubbles in it. You can always fill them in before you bake it.
12. With the wax out, put it in the oven and bake it at 325 or so for at least a 45 mins.
13. tape the two halves together with layers of duct tape. they should line up nicely.
Put the mold in a pan so you wont waste lead if your mold leaks.
14. Now you are ready to cast the metal (lead, in this case).
Do this OUTSIDE; none of the gasses that come from molten lead are good for you. Wear a respirator/gasmask if you have one.
There is a good tutorial on casting lead at http://www.spudfiles.com/forums/viewtopic.php?t=6613& , which uses a portable gas stove to melt lead. I did mine on the grill.
Heat the lead up in the soup can and use your pliers/ tongs to pour it in(Are you wearing your gloves and safety glasses???)
!!!!!!IF IT STARTS BUBBLING VIOLENTLY IN THE MOLD, STOP POURING AND LEAVE THE AREA!!!!!!!
Bubbling usually means you have moisture left in the mold, which can sometimes result in an explosion. Wait until it cools down, remove the lead, and bake it again.
But if all goes well, fill it to the top and let it solidify (this took 20 mins for my 2" ball)
15. After the mold is fairly cool remove the tape and open it gently. Unless you waited a really long time, it will still be hot but you can pick it up with tongs/heat-resistant gloves and dunk it in water.
Now just cut off the extra lead with your saw and file, and smooth out any rough spots (Keep track of where your lead dust is falling, it's really bad for the environment)
TIPS:
--Your mold will probably last longer than one casting before it cracks beyond use (for lead anyways). Put it in a pan to contain the metal should it break
--while your pouring. Mine lasted 5 castings before I broke it by accident.
--Tire weights are a good source of lead. My tire place was nice enough to give me 20 pounds of them for free after I used the "I've got a Science Project..." line.
--If, for some reason you want to make a copper projectile, you're going to need somethin better than a soup can. Steel melts at a high temp than copper but I have never been able to keep a can together long enough to melt a usable amount of copper. Molten salt will also eat though cans quickly.
I probably should have said this earlier, but I thought it would be common sense:
DON'T SPILL MOLTEN LEAD IN YOUR GRILL!!!
Lead + hamburger = brain damage.
