In the modern world you have a lot of options for keeping yourself safe from harm. Whether you prefer a Taser or you carry a can of pepper spray mace in your pocket, it isn’t strictly necessary to harm an attacker to keep yourself free from harm. But for those who feel they need lethal force on their side, and they’re willing to do the paperwork to get a concealed carry permit, there is always the option of a gun. Whether you prefer a gleaming semi-automatic or the old, reliable revolver there’s just nothing like having a sidearm ready to back you up. Of course whether you’re using a .357 Magnum or a .50 Desert Eagle the mechanics are all, relatively, the same.
Turn back the clock a few hundred years. Back before the gang wars of Prohibition, back before the Old West and Samuel Colt, and even back before the pirates who sailed the Spanish Main. If you back up to 1350 A.D., you’ve found roughly the place where guns first became accepted. Only half a dozen decades after William Wallace spit in the teeth of Edward the Longahanks, Western armies were fielding heavy guns fired from soldiers’ hands or set atop massive, wheeled carts. Today we refer to these primitive guns as cannons. Simple and efficient, the physics of how modern guns work can be seen in this firearm ancestor.
You start by pouring a load of gun powder down the cannon mouth, packing it against the rear. You follow that down with the cannon ball, and you tamp that down so the powder and ball are snuggled in close. Then you poke a fuse into the powder through a small hole at the rear and light it. The fuse carries fire to the gun powder which ignites in a chemical reaction. Since the blast is contained by the cannon it escapes towards the mouth and as it goes the force pushes the heavy cannon ball up and out to fire it into an oncoming army. Generally speaking the bigger the blast, the more force created and the further the round will go. This initial technology came in the form of field or hand canons, both of which were heavy and often unpredictable.
You move up through the years, this basic idea is still how guns work. Modern cartridges, what most people think of as bullets, are actually made of all the necessary parts. The brass shell is loaded with a gunpowder charge, and then the lead bullet which has been carefully shaped to the barrel it’s meant to be fired from is pushed 1/4 or so of it’s length down the cartridge. The back of the brass shell has a small hole that’s filled with a primer, which will react when struck by a hammer. The primer ignites the gun powder, the gun powder explode and forces the bullet down the barrel of the gun towards the target. With rifled barrels, those that have a rifling pattern inside, the bullet develops a spin that makes it more accurate. But aside from this, and the torpedo-like shape of modern bullets, it’s still just a hand cannon.
No matter how technology has changed, this principle has remained the same. Whether you’re talking about advanced systems to fire hundreds of rounds like Metal Storm, the hollow point bullets used by American law enforcement or even the flintlock and matchlock weapons used by soldiers hundreds of years in their graves, the physics are always the same. Compressed air and gas, generated by a chemical explosion that can be aimed at your enemies who, hopefully, aren’t wearing bullet proof vests.
“How Flintlock Guns Work,” by Marshall Brian at How Stuff Works
“How Does a Gun Work?” by John Albers at eHow