Did cannonballs explode?
In movies showing battles from the Civil War and earlier conflicts, cannon-fired projectiles inevitably send up dirt and smoke and flailing stuntmen upon impact. It makes a nice visual and is probably easier to stage than an iron ball bouncing murderously through a division.
In reality, an array of both exploding and solid projectiles were used in the Civil War and for centuries before, but solid shot predominated until around the1850s.
The earliest cannons, developed in 1300s, fired nothing but solid objects — stone balls. The following century weapons makers did develop hollow iron balls filled with gunpowder and fitted with a fuse that had to be lit just before firing. But the difficulty in handling these primitive time bombs and in getting them to explode at the target made them both dangerous and unreliable. To minimize the danger of their blowing up in the cannon’s barrel, these lit-fuse balls were used mainly in quick-loading, wide-bore, stubby-barreled cannons called howitzers or with drop-and-fire “mortars,” which looked like the World War II-era weapon of the same name only much larger.
Over the centuries, weapons makers devised a great variety of solid-shot combinations and techniques. The one-two punch of stone and iron balls spelled doom for castle walls. At close range, cannons were often used like sawed-off shotguns to fire bunches of smaller balls, devastating to troops massed on level ground. At sea, ships often fired iron bars, chains and small balls to take down masts and rigging. Another trick was to heat a cannonball red hot in hopes of igniting a fire on deck or, better yet, landing one in the enemy ship’s magazine. Blasting a hole through the hull of the enemy ship by firing into the water normally didn’t work, however. The ball would skip off the surface.
Elongated solid projectiles called bolts were developed for use with rifled cannons, which had a spiral groove cut on the inside of the barrel to start the projectile spinning and improve accuracy. But round balls were the most common solid shot used in the Civil War, and those are what you see today welded into a pyramid shape and set next to a cannon in a town square.
Sources: Daniel A. Lindley and Keir Lieber, both Notre Dame assistant professors of government/political science; Dennis Showalter, professor of history, Colorado College; various reference works