breech bolt

breech bolt

[′brēch ‚bōlt]
(ordnance)
A mechanism which opens and closes the breech in a carbine, machine gun, rifle, and the like; designed to push a cartridge into the chamber by sliding action.
References in periodicals archive ?
Tenders are invited for Tender For Head Breech Bolt To Tend 2045.
Drop the hammer, remove the rear sight, re-cock the hammer and slide the breech bolt from the receiver.
As the employee turned the handle on the breech bolt holding the round, it was forced out at high speed by the trapped gas.
When the breech bolt is moved, the gun will jam with the bolt to the rear.
When a Benelli is fired, the mass of the breech bolt remains stationary while a carefully calibrated spring pushes against the rotating bolt head, forcing it into tighter engagement with its matching cuts in the barrel extension.
When the action-bar sleeve impacts against the front of the receiver, 5 ft-lbs of the 10 ft-lbs stored in the moving mass are put back into the equation and an instant later the breech bolt, still moving rearward, impacts against the rear section of the receiver, putting back the other 5 ft-lbs, thus satisfying Newton's Law.
Upon inspection, he determined that a GAU-8 Breech bolt firing pin had failed causing every seventh round not to fire.
Lockup is accomplished as twin lugs on the rotating head of the breech bolt engage shoulders on the inner wall of the barrel extension.
To quote Brophy, "Correct locking of the breech bolt and locking bolt into the receiver is essential, and if the parts are broken, jammed by dirt or rust, it is possible to fire these exposed hammer shotguns with the bolt not properly locked.
The same breech bolt assembly, NSN 1005-01-505-1035, is actually used on all the M16A2 and M16A4 rifles and M4/M4A1 carbines.