M16 bolt locking M16 bolt unlocking

Rotating bolt is a method of locking thebreech (or rear barrel) of a firearm closed for firing.Johann Nicolaus von Dreyse developed the first rotating bolt firearm, the "Dreyse needle gun", in 1836. The Dreyse locked using the bolt handle rather than lugs on the bolt head like theMauser M 98 orM16. The first rotating bolt rifle with two lugs on the bolt head was theLebel Model 1886 rifle. The concept has been implemented on most firearms chambered for high-powered cartridges since the 20th century.

Ferdinand Ritter von Mannlicher, who had earlier developed a non-rotating bolt straight-pull rifle, developed theSteyr-Mannlicher M1895, a straight-pull rifle with a rotating bolt, which was issued to theAustro-Hungarian Army. Mannlicher then developed the M1893 auto rifle which had a screw delayed bolt and later theMannlicher M1900 operated by a gas piston. This was an inspiration for latergas operated,semi-automatic andselective fire firearms (such as theM1,M14,M16, theL85A1/A2 and theAK-47/74) in which thebolt, upon contact with thebreech, rotates and locks into place, the lugs on the bolt locking into the breech or barrel extension.

Upon closing, the bolt goes forward intobarrel extension or locking recesses in the receiver, and then rotates; at this point it is locked in place. The bolt remains locked until theaction is cycled, either manually by the operator, ormechanically bydelayed blowback,recoil operation, orgas operation which then rotates the bolt and unlocks it from the breech so that it can be withdrawn in order to extract and eject the spentcasing, and the next round can bechambered. In gas operation, the gas port, which meters a portion of the combustion gases into the action in order to cycle the weapon, is typically located either midway down the barrel or near the muzzle of the weapon. In this way it functions as a delay, ensuring that the bolt remains locked until chamber pressure has subsided to a safe level.

Rotating bolts are found indelayed blowback,gas-operated,recoil-operated,bolt action,lever-action, andpump-action weapon designs. In some forms of delayed blowback, the rotating bolt is used as the delay mechanism: the bolt head rotates as the firing pin strikes, locking the chamber until the gas pressure reaches a safe level to extract. As the firing pin retracts, the bolt head turns anti-clockwise unlocking the breech.

• M1 Garand, gas-operatedsemi-automatic rifle^[1]
• M25 Sniper Weapon System,semi-automatic rifle, gas operated, air cooled
• Lebel Model 1886 rifle, bolt-action rifle
• Steyr-Mannlicher M1895, a straight-pull rifle
• M16, a gas-operatedrifle
• AK-47, a gas-operatedrifle^[2]
• Oerlikon KBA 25mm, gas-operated autocannon^[3]
• Imbel IA2, a gas-operatedassault rifle
• IWI Tavor TAR-21, a gas-operatedassault rifle^[4]
• Ruger Mini-14, a gas-operatedsemi-automatic rifle^[5]
• IMI Desert Eagle, one of the fewhandguns with such mechanism.
• Remington Model 8, a recoil-operated rifle
• Chauchat, a recoil-operated light machine gun
• Remington Model 7600, a pump-action rifle
• The Winchester model 1200, 1300,and Super-X (SXP) Pump Shotguns
• SIG-Sauer MPX, a gas-operatedsubmachine gun^[6]
• CMMG MkG, the first AR15 derivative to use radial delayed blowback operation.
• Browning BLR, alever action rifle with a rotating bolt
• L85A2, A variant of the L85A1
• S&T Motiv K16, a gas-operatedgeneral purpose machine gun

• Roller locked

• Computer Animation demonstrating rotating bolt in the M16
• Primer actuated M16 using rotating bolt