| 摘要 |
An upper receiver is provided for cooperatively engaging a lower receiver, wherein the lower receiver includes at least a trigger and a lower hammer. The upper receiver includes an upper sear movable in response to movement of the lower hammer, thereby permitting an upper hammer in the upper receiver to actuate a valve in the upper receiver and pass a motive gas to a firing chamber and thereby expel a projectile through a barrel of the upper receiver. |
