Most modern long guns are either rifles or shotguns. Both are the successors of the musket, diverging from their parent weapon in distinct ways. A rifle is so named for the spiral grooves (riflings) machined into the inner (bore) surface of its barrel, which imparts a gyroscopically-stabilizing spin to the bullets that it fires. Shotguns are predominantly smoothbore firearms designed to fire a number of "shot" in each discharge; pellet sizes commonly ranging between 2 mm #9 birdshot and 8.4 mm #00 (double-aught) buckshot. Shotguns are also capable of firing single solid projectiles called slugs, or specialty (often "less lethal") rounds such as bean bags, tear gas or breaching rounds. Rifles produce a single point of impact with each firing but a long range and high accuracy; while shotguns produce a cluster of impact points with considerably less range and accuracy. However, the larger impact area of shotguns can compensate for reduced accuracy, since shot spreads during flight; consequently, in hunting, shotguns are generally used for fast-flying game birds.