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An 18th century invention by Benjamin Robins allowing a more-pracitcal use of gunpowder in ballistics.

Up to and through the early 18th century, early-modern European gunners and their theories with gunpowder were shaky at best. They had no foundation for their preferences, and no rational explanation for how their designs with the explosive worked. With the advent of the ballistic pendulum, however, all this would change, leading to drastic improvements in all forms of the gun.


Gunpowder, it must be understood, was a relatively recent and under-developed technology in the late 18th century. European armies of the time used muskets, that, though cumbersome (especially in reloading) and innacurate, served their purpose well enough – if you fired at a line of advancing British, chances are you’d hit someone…somewhere.

In the 1400s, smiths innovated the use of “corned” gunpowder. They would mix gunpowder with water, to form uniformed cakes with the correct concentration of grain – some of it very coarse (the size of corn grains and thus the name), and others with varying sized kernels from medium to very fine. The gunpowder mills themselves could be powered by water, mixing huge batches relatively easily. This allowed for much safer processing of gunpowder (It’s always better when there are no explosions), as well as a cheap manner of manufacturing great amounts of it.

Late-medieval and early-modern gunners generally preferred fine gunpowder with handguns, medium grains with muskets and rifles, and large-corned gunpowder for cannons. They were correct in their choices, but as time wore on, little developments were made in the industry.

In fact, if anything, a counter-development took place, and by the mid-18th century, during the French and Indian War, the Europeans generally used gunpowder in a willy-nilly fashion – fine with cannons, large with muskets, etc. This made accidental explosions common, and also decreased the efficiency of use. Much ammunition was wasted because of scientific ignorance.

New Principles of Gunnery

In 1742, a British mathemetician named Benjamin Robins published New Principles of Gunnery, a work that told gunners exactly how much gunpowder, and of what kind, they should be using. How did he do it? With a ballistic pendulum.

Robins had the bright idea of hanging a wooden block from the ceiling by two cords. A bullet, fired into the wood, would swing the block up at its momentum, which could then be measured by the swing’s amplitude. This is a result of the law of conservation of momentum. Because an object’s momentum is the product of mass and velocity, and momentum is conserved, then mv = (m + M)V where “v” is the velocity of the projectile, “m” is the mass of the projectile, “M” is the mass of the block, and “V” is the velocity of the block.

This equation is then morphed so that the projectile’s velocity is expressed in terms of the block’s amplitude/momentum:



Being able to specifically measure velocity in relation to the gunpowder charge revolutionized ballistics. It was finally possible to determine the exact charge necessary for a specific effect; from then on, gunpowder use could be more efficient, ammunition conserved, and better guns invented. Despite the fact that this device has long been made obsolete, it is still in use in classrooms for experiments of momentum and energy.

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