Pellets

Although the BB is a single type of round projectile made of steel, the number of types of pellets available is enormous. In general, pellets have a shape known as diabolo which means that the front and rear sections are of larger diameter than the middle. One reason for this is to reduce the friction that would result if more of the pellet made contact with the barrel. Even though some airguns are rather powerful, the amount of work necessary to push the pellet down the barrel would be large if the pellet had a shape like a bullet.

Another feature of pellets is that they have hollow bases (the skirt area of the pellet) that are generally larger in diameter than the front section (known as the head of the pellet). This enables the skirt to effectively seal the bore against the pressure pushing on the base of the pellet while the friction on the head area is not too high.

The pellet velocity from any air rifle depends on the weight of the pellet. Heavier pellets simply can not be driven as fast as lighter ones. However, heavier pellets normally retain their velocity better as a result of their having higher ballistic coefficients. Even though initial velocity is lower, a greater percentage of that velocity is retained down range. Although a great deal of emphasis is placed on high muzzle velocity, pests are normally shot at some distance from the muzzle so the ability of the pellet to retain velocity is also important.

Wadcutter

Wadcutter or flat nose pellets have flat points that cut round holes in a paper target. This type of pellet is a good choice for general shooting

Domed

Round nose or domed pellets have a front section that is rounded which allows it to penetrate air better. Round nose pellets retain their velocity better than do wadcutter pellets. Also, they generally penetrate the target more deeply than wadcutter pellets which is an important consideration in hunting applications. Domed

Pointed

Pointed pellets have a nose that is more sharply pointed than the domed type, but they do not have the sharp points that are common of ammunition is intended for use in firearms. The pointed pellets retain their velocity even better than do the domed variety, but the difference is not very great.

Hollow Point

There are pellets that have hollow cavities in the nose. This facilitates expansion when the pellet impacts a target which is important when the most effective impact on a soft target is desired. Hollow point pellets work well when shooting small pests where a heavy blow but little penetration is required.

BBs

The BB is a classic airgun projectile. For many years, BBs were made of lead, and lead "rounds" as they are called are still available for use in certain types of guns. However, BBs made of steel are almost universally used in air rifles today. To prevent corrosion, BBs are given a coating of another metal such as copper. The number of BBs manufactured and sold is enormous.

Although traditionally used in airguns of low power, BBs are far from harmless. A steel BB does not deform when it impacts a target so it can penetrate soft targets. A real problem associated with the use of steel BBs is that when the steel ball strikes a solid target, it may be compressed very slightly because steel has some elasticity. This resiliency can cause the BB to be propelled backward toward the shooter at high velocity. Steel BBs ricochet badly unless they are fired against a soft backstop such as a bag of newspapers. Even then folded newspapers should have a few loosely crumpled papers in front so that the BB penetrates these and is stopped by the folded papers but does not bounce back. Never underestimate the ability of a BB to ricochet!

In addition to some low powered guns that are designed to fire only BBs, some models such as the Crosman 760, 66, and 2100 are "dual ammo" guns that also fire pellets. These rifles function as repeaters with BBs, but can be used only as single shot rifles with pellets. Although BBs are much less expensive than pellets, they have some disadvantages. First, a steel BB can not be designed to fit tightly in the bore. As a result, accuracy of a particular rifle is not as good when shooting BBs as when pellets are used. Pellets are made of lead or a lead alloy so they are soft. They can be made to fit the bore by being swaged slightly as they are fired. Therefore, they fit the rifling better, and the result is better accuracy. Another disadvantage of firing steel BBs in a rifled barrel is that the BBs do not engage the rifling but rather ride on top of the ridges. Prolonged use of BBs in a rifle barrel can cause the tops of the rifling ridges to be worn off because unlike a lead pellet, a BB is as hard as the rifle barrel itself. If this happens, the rifle probably will not shoot as accurately with pellets as before the abrasion occurred. BBs are best used in airguns with smooth bores.

Airsoft BBs

There is a tendency to call any spherical projectile a BB, but strictly speaking the BB is a metal ball having a diameter of approximately 0.17 inch. Airsoft guns fire spherical projectiles made of plastic and measuring about 6mm (approximately 0.24 inch) which are often referred to as BBs. Made of plastic, these balls have low density so they lose velocity rapidly. These BBs are designed to be fired at velocities of 400 ft/sec or less from guns that are powered by a single pump, CO2, or an electric motor powered by a battery. The airsoft guns are designed for short range fun shooting. In general, high accuracy is not a trait of airsoft guns, though there are exceptions with many of the premium models.