The M4 carbine is a lightweight, air-cooled, gas-operated rifle used primarily by the United States military. It is a variant of the M16 rifle and features a shorter barrel, making it more maneuverable in close quarters. The M4 is chambered for the 5.56x45mm NATO cartridge and can be fired in both semi-automatic and fully automatic modes. Equipped with a collapsible stock and a Picatinny rail system, the M4 allows for the attachment of various accessories, such as scopes and grips. Its versatility and reliability have made it a popular choice not only for military use but also for law enforcement and civilian applications.