Yamaha K-31 Service Manual download pdf (Page 31)

35, 36

IV. Function

1. Trigger Mechanism and Rifle Discharge

(Fig. 17)

11 When the weapon is ready to fire, the bolt is closed and locked, the trigger mechanism is armed

(normal position. See Fig. 17)

The pressure placed on the trigger causes the trigger sear to lower; this trigger movement is paused

as the rear trigger boss comes into contact with the receiver. (stop point).

The lip of the trigger sear then holds the Cocking Piece Sear lightly such that a very slight

pressure on the trigger is all that is required to lower it completely.

At the moment that the cocking piece sear is freed from the restraint of the trigger sear, the

cocking piece, under the pressure of the firing pin spring, is projected forward. The firing pin

strikes the cartridge primer and it ignites.

2. Unlocking and opening the bolt

(Fig. 18)

12 When the handle of the cam follower is pulled to the rear, the cam follower pin slides in the

longitudinal slot in the cylinder and at the same time along the helical slot in the locking sleeve.

The cam follower pin arms the firing mechanism by moving rearward the firing pin and the

cocking piece and compresses the firing pin spring. The aft pocket of the helical slot in the

locking sleeve ensures that the cam follower pin will not be pushed forward by the firing pin

spring. The firing mechanism is armed in this fashion.

Fig. 17

A. Mq. Mod. 31

The three trigger positions

1. Normal Position

2. Position after trigger first stage (sear ready to release)

3. Post Weapon Discharge

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Yamaha K-31 Service Manual Page 31