Humans have a long history of being creative with their weapons. Necessity is the mother of invention, and there's no necessity greater than not dying because you can't shoot back. As a result, humans have come up with more than their share of surprising weapon systems and ammunition – with varying degrees of success.
Here are the 4 weirdest ammunition types ever used
The tround, short for triangular round, was designed by David Dardick in the mid-1950s for use in his open-chamber line of weapons. It may sound strange, but the open cylinder allowed rounds to be fed into the weapon via the side as opposed to the front or rear. But the real draw was that triangular rounds would allow a weapon's user to carry fifty percent more ammunition in a case.
Trounds also allowed for different cartridges to be used in place of the tround ammo, where the triangular casings were used as chamber adapters.
The gyrojet weapon was developed by an engineer who worked at Los Alamos who was trying to scale down the bazooka concept to create an antitank weapon that was also compact. The gyrojet was a rocket launcher shaped like a gun firing ammunition that actually accelerated as it got further from the weapon.
It had no recoil, could be fired underwater, and could penetrate armor at 100 yards. The only problem was that its accuracy was so terrible that hitting anything at 100 yards was problematic.
The Puckle Gun was an early development in the history of automatic weapons. It was a single-barreled flintlock weapon that was designed to keep boarders from getting onto another ship. The weapon was never actually used in combat, but it featured two rounds of ammunition; circular rounds for fighting Christians and square bullets for shooting Muslims, because square bullets apparently cause more damage. According to the patent, its purpose was to "convince the Turks of the benefits of Christian civilization."
Lazy Dog missiles
What you see is what you get with the lazy dog ammo. There's no cartridge, no propellant, no explosive – just a solid piece of metal attached to fins. They were dropped from high altitudes en masse and by the time they reached the ground were able to penetrate light armor.