Explain the steps of how modern ammunition fires

Modern firearms use the same principles as muzzleloading firearms. The ignition and burning of gunpowder create pressure. This pressure propels projectile(s) down the bore and out of the muzzle. The first modern firearms used black powder. Since about 1890, modern firearms are designed to use smokeless gunpowder. Smokeless gunpowder creates greater pressures and should not be used in firearms designed for black powder. Watch what happens when the trigger is squeezed on this bolt action rifle.