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Open 9 Major MSH


tanfoglio1911

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43 minutes ago, Aircooled6racer said:

Hello: 17lb ISMI in both. 8-10lb ISMI recoil spring for 9mm depending on load and personal preference. Thanks, Eric

 

Thanks. I used 9 lbs on my 40 open but might try it first before going down to 8 lbs to my new 9mm upper.

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With a SS firing pin, I won't go lower than 17 lb for a mainspring.  With a Ti firing pin, you will have to go higher.  Going heavier for insurance does not change trigger pull that much.

 

For example, one pistol had a 16-17lb MS and worked perfectly until I put a 22 conversion on it.  Then I had 20% FtF issues.  I replaced the 16-17 with a 19 and the problem disappeared.  Trigger pull before the switch was exactly 2.5 lbs.; after it was 2.62.  A minor adjustment to the sear spring and it would be back to 2.5.

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2 hours ago, zzt said:

With a SS firing pin, I won't go lower than 17 lb for a mainspring.  With a Ti firing pin, you will have to go higher.  Going heavier for insurance does not change trigger pull that much.

 

For example, one pistol had a 16-17lb MS and worked perfectly until I put a 22 conversion on it.  Then I had 20% FtF issues.  I replaced the 16-17 with a 19 and the problem disappeared.  Trigger pull before the switch was exactly 2.5 lbs.; after it was 2.62.  A minor adjustment to the sear spring and it would be back to 2.5.

 

I am not sure yet if the gunsmith will put Ti of SS firing pin, but I will take note of this. Thanks a lot.

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