Gunsmith ques. - how does the bolt cock the trigg.

l-girl

July 24, 2002 09:55

I have a Japanese Type 38 Arisaka in 7.7 which functions perfectly. I have also obtained a second one that the bolt will not cock the trigger. When I exchange the bolts, the other bolt will cock the trigger.

Comparing the two bolts, everything looks the same except the bolt that doesn't work has a small round opening on its underside whereas the bolt that does work has a larger, oval opening. Is the difference in the openings causing the problem? I am wondering if the wrong bolt is on the Type 38 that won't cock (maybe a Type 99?)

My disassmembley manuals are no help on this.

Thanks.



Best regards,Rich

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  captkirk3@dslextreme.com

  July 24, 2002 12:58

  The SEAR engages the Firing Pin, Holding it the Cocked position in the Bolt Body...The TRIGGER engages the Sear and when Pulled allows the Firing Pin to Travel Forward and Strike the Primer in the Cartridge causing it to Ignite the Powder Charge therein and releasing expanding Gases which in turn Propell the Projectile in the Cartridge out the Barrel and towards the Target....[hopefully]...As for the Sear not engaging the Firing Pin in Bolt 'B' I believe its a Bolt from another gun...You might place a Request for Jap Bolt Differances on the Forums...There are numerous Collectors out there of Jap Rifles...I'm sure someone will be able to help you.....Best
  
  Captain Kirk, Tech Staff

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  v35

  July 24, 2002 18:06

  Japanese service rifles cock on closing of the bolt. If you have one that cocks on opening, it has been modified by welding a cocking ramp on the bolt. On a cock-on-opening, bolt action the firing pin is cammed to the rear by a ramp on the bolt. The firing pin is captured by a fore and aft, slot in the receiver and can only go forward or rearward as the bolt handle is moved. As the bolt is lifted,the firing pin moves rearward compressing the firing pin spring and passing over the spring loaded trigger sear which pops up, trapping it to the rear.
  When you pull the trigger the sear moves downward, releasing the firing pin which is driven forward by the firing pin spring.
  As you examine both bolts side by side, you will see the difference in the cocking ramps. The longer ramp bolt, cams the firing pin further rearward.
  Cock on closing military rifles require less effort and in general are better in rapid fire. The British Enfield is a good example.

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  v35

  July 24, 2002 18:26

  In rereading your question are you saying the second bolt cocks but will not fire? If this is the case, there is a pin (part of the trigger assy)that rises as you pull the trigger. This pin is a safety feature,designed to go into a hole or slot in the bolt body only when the bolt is fully closed, allowing the sear to disengage the firing pin. If you want to adapt the second bolt to the rifle, you have to alter the opening to allow the pin to rise in the hole.
  Don't reduce the pin height as it would void this safety feature.

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