Here are 3 early attempts at automatic weapons

The search for an effective rapid-fire weapon, particularly in the latter 19th century, took on some innovative designs, most of them of dubious battlefield utility and rarely employed. All this changed when the U.S. Army adopted the famed Gatling gun in 1866, which could reliably fire up to 400 rounds a minute and had already proven itself in small quantities during the Civil War. John Gatling -- ironically a physician -- had suddenly made warfare far more deadly.

Here is a look at some early attempts at automatic weapons before Gatling turned them into the staples of warfare they are today.

1. Repeating Crossbows

The Polybolos was a large repeating ballista dating back to the 3rd century B.C. It was supposedly the invention of a Greek engineer named Dionysus, who worked at the large arsenal on the island of Rhodes. Fed by a large wooden magazine holding several dozen bolts of the weapon's cradle, it allowed its crew to crank a large windlass back and forth, allowing it to achieve a far greater rate of fire than conventional ballistics.

A replica built by the Discovery show "MythBusters" proved that it could have been a very feasible weapon, but would have suffered from severe reliability problems.

A device similar in concept called the Chu Ko Nu was in use by Chinese soldiers as early as the 4th century B.C., but it was conceived more as a rapid fire light crossbow. Holding up to 10 bolts, the soldier could rapidly crank a handle and fire every couple of seconds, an astonishing rate of fire for a weapon at the time. The bolts were light and its range was short, but it was intended for mass formations and made up for its lack of power with volume of fire. To increase lethality, its bolts were sometimes coated in poison.

2. Coffee mill gun

The American Civil War saw widespread experimentation in weaponry, and among the most sought was a rapid fire battlefield gun that could support the infantry. The "coffee mill," or Agar gun, the namesake of it's inventor Wilson Agar and mounted on a light artillery carriage, was one such attempt. Standard .58 rifle cartridges were loaded in special steel tubes and were placed in a large hopper on top of the weapon. A hand crank fed the cartridges and allowed a rate of fire of up to 120 rounds per minute. The feeding mechanism resembled an old-fashioned coffee mill, giving it its nickname. President Abraham Lincoln witnessed a demonstration and was very impressed by the weapon's performance, and a small number were purchased by the Union Army.

Despite its impressive rate of fire, the weapon had serious disadvantages. Reloading the steel tubes was cumbersome, making keeping up the rate of fire difficult, and their loss made the weapon useless. The feed mechanism was vulnerable to jamming, and the weapon was highly prone to overheating. Its range was no greater than a standard rifled musket. Though it saw some action, its flaws, and the few number purchased ensured it played only a minor role in the war, and it was quickly replaced by the far more effective Gatling gun.

3. Mitrailleuse

One approach to rapid fire was the clustering of large numbers of single-shot barrels together that were fed by a single large breach, firing in sequence before being loaded in again. The Mitrailleuse, from the French word for grapeshot, was the pinnacle of this concept. The original design came from it's Belgian inventor Captain Fafchamps in 1851, but many variants saw service in the French Army leading up to the Franco-Prussian war.

Carrying up to 50 barrels and mounted on an artillery carriage, the weapon was breech loaded using large steel blocks studded with ammunition. A small crank was then turned to manually fire each round. A skilled gunner on some types could achieve over 100 rounds a minute. The Reffye variant which was most commonly used by the French used 13mm rounds with a range of over 2,000 yards. Unlike a modern machine gun, it was used more as artillery, with all its ammunition being expended on a single point target.

By the time the Franco-Prussian war broke out, the French had slightly more than 200 Mitrailleuses in service. The Prussians, despite having few rapid fire weapons of their own, were not particularly impressed by their enemies wonder weapon. It's inability to be targeted quickly, and it's rapid expenditure of ammunition onto a single target, rendered it tactically inflexible and redundant to conventional artillery. The small numbers deployed also limited the weapon's effectiveness. After losing the war, the French phased the Mitrailleuse out.