Pellets are generally wasp-waisted cylinders made of lead or non-lead alloys and provide the highest accuracy in the rifled barrels of adult precision air rifles and air pistols. Pellets of various calibers are available in flat-nose, round-nose, pointed, and hollow-point configurations.

BBs are round balls generally made of steel (although lead BBs are available in some calibers).

There are two main types of airgun ammunition: pellets and BBs.

There are several factors to keep in mind when selecting an airgun caliber:

Accuracy -- Every airgun will have a particular pellet that it likes and will produce the best accuracy. Having a wide spectrum of pellets increases the odds of finding a pellet that will work well in a particular airgun. If accuracy is the sole concern, .177 offers the greatest variety of pellets, with .22 would be close behind.

Weight – The lightest pellets (between 4 and 5 grains) available are .177, but it is rare to find a .177 pellet heavier than about 16 grains. By contrast, .25 caliber pellets are available as heavy as 34.9 grains and usually not lighter than 17.7 grains.

Speed and trajectory – Shot from the same airgun powerplant, a light pellet will generally fly faster than a heavy pellet. At any given velocity, however, a heavier pellet will carry more energy down range and will usually retain it longer than a light pellet that was launched at the same speed. Because of these considerations, for a really fast, flat trajectory out to, say, 50 yards or so, .177 would be a good choice. But for greater ranges, a bigger caliber with heavier pellets would be more appropriate.

Power and impact – Launched at equal velocities, a heavy pellet will typically deliver more foot-pounds of energy to the target than a light pellet. If velocity and accuracy are equal, for greater hitting power, chose the heaviest pellet and largest caliber.

Wound ballistics – Bigger pellets produce bigger holes, but smaller diameter pellets often penetrate deeper.

BBs are round balls generally made of steel (although lead BBs are available in some calibers).

Currently, there are four main calibers in airguns. The most popular is .177. It is used for both target shooting and hunting and offers the greatest selection of pellets. The next most popular is .22, which is used for both hunting and long-range target shooting and is available in a wide variety of pellets. The .25 offers more power, bigger wound channels, and heavier pellets. It is gaining popularity but offers fewer pellet choices than .177 and .22. Bring up the rear is .20 caliber. It has its enthusiasts, but appears to be dropping in popularity.

Big-bore calibers -- .30 caliber and above – are rising in popularity for hunting medium and larger game but offer fewer pellet choices.

Steel BBs ricochet readily. As a result, BB shooters need to avoid shooting at hard surfaces and make sure they use eye protection.