Yamaha K-31 Service Manual download pdf (Page 33)

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13 During locking sleeve rotation, the locking lugs exit the locking lug slots in the receiver and stop

rotation at the entrance of the locking lug guide grooves that run along the length of the inside of

the receiver; the bolt is, in this position, unlocked and may be pulled freely to the rear up to the

bolt stop.

At the same time, the extractor pulls out the empty case and the case is ejected at the point where

it hits the ejector.

The upper cartridge in the magazine is the raised into position by the magazine spring and stops in

front of the bolt

3. Closing and locking the bolt

14 When the bolt is pushed forward, the locking sleeve turns slightly as guided by the angled surfaces

on the locking lugs. The same movement frees the cam follower pin from the aft pocket in the

helical slot in the locking sleeve. The lip of the trigger sear then restrains the cocking piece sear.

The firing pin spring is remains compressed in this fashion. As the cam follower place is pushed

further forward, the cam follower pin, guided by the helical slot in the locking sleeve, turns the

locking sleeve. The locking lugs turn into the locking lug slots in the receiver and the bolt is

locked.

A bolt that is not completely locked exposes the shooter to the risk of accident, also the risk of

damaging the cam follower pin (see appendix IV of the present regulation “Instructions for

damage avoidance to small arms”). During bolt closure the bolt pushes the top cartridge in the

magazine forward and into the chamber. The extractor claw then snaps into the lip of the cartridge

case.

15 When all of the cartridges in the magazine have been fired, it is not possible, then, to close the

bolt; the shooter is thus made aware of the need to reload.

4. Safety

16 When the cocking ring is pulled rearward and turned to the right, the cocking piece sear can be

placed in the safety slot in the bolt plug. This slot is shorter than the firing slot; it is for this reason

the firing pin cannot protrude past the face of the bolt cylinder. All contact with the cartridge

primer is thus prevented. The cocking piece sear falls into a pocket the keeps the bolt from

opening accidentally.

V. Malfunctions and Repairs

17 Most of the time, malfunctions are caused by poorly executed bolt operation, by poor

maintenance, or from inadequate inspection.

If malfunctions or misfires occur during operation and handling a loaded weapon is required, it is

necessary to proceed in the following fashion:

a) Secure the weapon by turning the cocking piece sear into the safety slot.

Open the bolt and remove the cartridge from the chamber.

b) If the bolt can be opened easily:

-Load and close the bolt,

-Inspect the cam follower plate to ensure that it is pushed all the way forward.

-Recock the weapon and continue shooting

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Yamaha K-31 Service Manual Page 33