Marble

Marbles are good solid projectiles, that can penetrate hard targets like wood and sheet metal. They are cheap easy to find and come in a range of sizes. The most common dimensions are 1/2, 5/8, 7/8 and 1 inch, or 12, 16, 22 and 25 mm. Larger marbles exist but are often too costly to be used in day to day shooting.

The manufacturing tolerances of marbles are often quite wide, so not all 16mm marbles will fit in a 16mm barrel for instance.

A marble hitting a hard target (such as a rock) is often crushed to harmless sand, but there are chances of getting sharp splinters and ricochets, and appropriate care should be taken. Because if their relatively consistent shape and size marbles are good projectiles to use in cannons with automatic loading mechanisms.