A bullet is an elongated metal projectile fired by a pistol, rifle, or machine gun. Bullets are measured by their caliber, which indicates a gun barrel's interior diameter or bore. The first bullets were round lead balls loaded down the muzzle of smoothbore weapons and propelled by the ignition of a physically separate charge of black powder. Modern bullets were developed in the 19th century for small arms with rifled barrels. These rifles have a system of spiral grooves cut into the interior surface of the gun's bore, imparting spin to the bullet during its trip down the barrel. The spin helps a bullet to maintain a point-forward attitude in flight; an elongated bullet with a pointed tip is aerodynamically superior to a round ball. It sustains its velocity much better in flight, gaining accuracy and range.
Very early in the evolution of humans, we discovered the value of projectiles. Back in the day, we threw rocks at various animals that looked good for dinner and at each other in anger. Then we tied the rocks to sticks and invented a way to club critters and sometimes people senseless to subdue them; many died. As we progressed or regressed, we discovered ways to launch our projectiles with slings and catapults. Early in the 17th century, the muzzleloader was invented. Depending on the particular gun and the user's experience, it could take anywhere from twenty seconds to two minutes to reload a muzzleloader and get off another shot; a proficient sharpshooter could fire three rounds per minute. Fast forward to today, and the AK-15 has a cyclic rate of fire of 700 rounds per minute, about 233 times faster than the old blunderbuss.
From that first hand-thrown rock to today's assault-style weapons, the projectile, or bullet, had only one purpose; to render the target unconscious at best or dead in many cases. If one accurately aimed round ball can kill one person in twenty seconds, we can now theoretically kill 233 people in the same twenty seconds with modern bullets. That kill rate is not likely to happen, but that's what the evolution of the projectile has produced.
The rock and bullet are both lethal. The speed at which we can dispense these deadly projectiles is a big difference. The real question facing society is the need for the average person to have access to weapons with this level of killing power and when and where they should be permitted to carry these weapons; do we need one of these to go shopping? Are they legitimate hunting rifles? What sort of game requires the ability to fire 700 rounds per minute?
Are we tired of going to the funerals of children? Does it make more sense to issue bulletproof backpacks to our kids so they can attend school rather than to manage the access to and transport of guns with military firing capacities? It's our society, our lives, and the lives of our children and loved ones; how do we want this to play out going forward?