Before purchasing ammo online, consider what type of ammunition works with your existing rifle, shotgun, pistol or another firearm. The caliber of ammunition indicates the internal diameter of each bullet's barrel and offers an easy way to determine whether a certain type of bullet will fit in your gun. A common caliber is .22 and is often followed by letters, such as .22 L and .22 S, which indicate that the bullets are designed to work with long-barrel and short-barrel rifles, respectively. To ensure a kill shot when hunting big game like caribou or deer, choose hollow-tip ammunition that allows the bullet to expand upon impact, optimizing internal damage. Bullets with a full metal jacket are ideal for shooting fast-moving targets since their casing lets them travel faster. By selecting appropriate ammunition for your firearm, the chance of jamming is greatly reduced.