The M14 adopts the gas guide working principle. Garand pioneered the gas closing and expansion gas guide device on the M14 and obtained a patent. The characteristic of this gas guide system is that it can automatically close the gas guide hole and limit the Gunpowder gas entering the gas cylinder. The gas guide device is located under the barrel and consists of a gas hoop, a gas hoop top plug, a piston barrel, a piston, a bolt frame and a recoil spring. The piston has a short stroke (approximately 37mm), and the rear half of the piston is a cuboid that rests against the bolt frame; the front half is cylindrical with an annular groove on the surface. The machine frame is hollow and equipped with a recoil spring. There is a closing valve on the right rear of the gas hoop, which can close the gas hole to launch rifle grenades.
The bolt is flat cylindrical, with a guide wheel at the front right end. The guide wheel is stuck into the guide groove on the bolt frame. The frame drives the bolt forward and backward in the receiver through the guide wheel. There is a shell pulling hook and an ejection rod at the front end of the bolt. The firing pin is located inside the bolt. The charging handle is on the right front of the receiver and is connected to the bolt through a connecting rod. When the last round is fired, the bolt will be held by the empty chamber on the left side of the receiver.
The firing mechanism of the M14 evolved from the M1 Garand rifle. Most of the parts are similar, including the double-hook hammer, trigger and trigger rod (first sear) and the first sear. The second resistor with resistor spring at the back, etc. The entire firing mechanism is installed at the rear of the receiver and is fixed by the safety pin. The safety switch is similar to the M1 Garand and is located in front of the trigger guard.
There are guide rails on both sides of the receiver that guide the movement of the bolt. There is also a beam inside the receiver with a gap in the middle. In this way, when the bolt has not yet reached the rotational locking position, even if the hammer is accidentally released and strikes the firing pin, there will be no risk of misfire. Because the crank protrusion at the rear end of the firing pin is blocked by the receiver beam, it cannot move forward even though it is hit. Only when the bolt is indeed locked and the rear crank of the firing pin is exactly located at the gap in the center of the receiver beam, can the firing pin strike the primer.
There is a charging handle guide groove on the right side of the receiver, a magazine groove at the front and bottom, a trigger seat fixing groove at the rear and bottom, and a bridge clamp guide groove above, which can be used with a bridge above the ejection port. The clip presses directly against the magazine. There is an opening on the lower right side of the USGI receiver for the speed control handle. The M14 speed can be removed when not needed and replaced with a speed lock. The selector lock of the M14 is a small part used to replace the selector handle. When the selector lock is installed on the M14, the selector lock is fixed in the semi-automatic position and cannot be converted to automatic shooting. However, as long as the selector lock is removed and the selector operating handle is reinstalled, the M14 can still choose the shooting mode. There is no speed reducer on the commercial semi-automatic M14 receiver, so the mounting hole for the speed control handle is also eliminated. This is a way to distinguish USGI receivers from commercial receivers.