A carbine is a type of long gun that has a barrel shortened from its original length. Most modern carbines are rifles that are compact versions of a longer rifle. Compared to submachine guns, carbines have a greater effective range and are capable of penetrating helmets and body armor when used with armor-piercing ammunition. The term "carbine" covers lighter weapons (generally rifles) with barrels up to 20 inches (510 mm) in length. These weapons can be considered carbines, while rifles with barrels longer than 20 inches (510 mm) are generally not considered carbines unless specifically named so. Conversely, many rifles have barrels shorter than 20 inches, yet are not considered carbines. The primary advantage of a carbine over a pistol using the same ammunition is controllability. The combination of firing from the shoulder, longer sight-radius, three points of contact (firing hand, support hand, and shoulder), and often a stock that fits the shooters shoulder all contribute to better accuracy and control.