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 being 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.

Use and Target Performance

The manufacturing tolerances of marbles are often quite wide, so not all 16mm marbles will fit in a 16mm barrel for instance. If you go to the store to buy marbles, it is suggested to bring a piece of your barrel to test fit your ammo.

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 of their relatively consistent shape and size marbles are good projectiles to use in cannons with automatic loading mechanisms.

Specifications

The following sizes are common for marbles both in the US and abroad. 1/2, 5/8, 7/8, or 1" (12, 16, 22, or 25mm)

The average density of glass is ~2.4-2.8 g/ml. This may vary slightly from the density of your marbles, do to manufacturing and glass content differences.