How to make lead projectiles
Lead bullets are cast in molds, as was common in ancient times. Since lead fumes are poisonous, the whole process should take place outdoors and the lead should not be heated more than necessary. The following video shows the casting process: https://www.youtube.com/watch?v=Xs5uxvzfU1c
The mold can be made from plaster, for example. To do this, pour the mixed plaster into a container and wait a short time until it has thickened slightly.
Next, push a bullet halfway into the plaster and leave it there.
After the plaster has set, cover the surface with talcum or petroleum jelly. Then, pour another batch of plaster into the container to make the second half of the mold.
After this has set, too, you can remove the mold from the container and take it apart carefully. Remove the blanks and carve a channel into the the mold halves through which you will later pour the molten metal. Add venting channels through which the air can leave the cavities.
Before using the mold, you should bake it, to remove as much moisture from it as possible. Then assemble the mold and secure it e.g. with clamps. The two halves have to fit tightly, or otherwise the liquid metal might flow out.
Now pour the molten metal in one go into the mold. Do not look into the mold from above, as moisture or trapped air can violently expand and propel the molten metal back out of the mold!
After waiting briefly, the metal will have solidified and can be removed carefully from the mold using a pair of pliers. Remove any excess material with cutting pliers and hammer the burrs smooth. Especially with lead, which is poisonous, you should not use a file or sand paper!
Instead of lead, you can also use tin or zinc. They have a lower density than lead, but are not poisonous. In ancient times, bronze was used as well for casting sling projectiles. However, it has a substantially higher melting point.
