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Old September 22, 2008, 08:40 AM   #1
Harry Bonar
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Growing trigger pull weight

Sirs;
Last week I was given a Caspian frame (factory drilled and tapped for their mount) and a slide (no markings whatever) by a friend for whom I did some milling work.
I had enough parts to complete the gun. Everything was O.K. until I got to the Trigger!
(Kart bbl, S&A nag well, Videki trigger, matted & bordered slide and frame, new match bushing - in other words "full House."
I started out with my normal trigger job on my Ron Power trigger jig and a new combat hammer and got a 3# pull - very good). However, after testing the trigger pull after some dry firing it increased to 7#! Why?
I've never had this happen! Several times it did this and I worked on this pistol for several days till I finally installed a behlert hammer and an old style Colt sear of proper length (dressed, of course) and now have a 5# pull that has remained uniform.
Has anyone ever experienced a trigger pull that would increase like this - I can only think that the hole spacing was off?
Harry B.
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Old September 22, 2008, 12:23 PM   #2
James K
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I can't be sure, but I suspect the hammer was on the soft side, or work on it cut though case hardening. In any case, normal firing causes the hammer to drop on the sear very quickly, and the sear cut into the hammer notch, leaving a groove that increased the trigger pull. If that is the case, examination of the hammer notch under magnification may bear it out.

Jim
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Old November 9, 2008, 02:22 AM   #3
JMBstudent
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Harry,
I expect replacing the hammer has resolved the growing pull issue.
I agree with Jim, it is likely caused by a soft hammer or sear.
Have you had the opportunity to closely inspect the parts?

A separate comment about pin hole locations.
I layed out the pivot pin holes at ten times normal size to understand the true relationship between the hammer and sear.
Obviously pivot holes not parallel, undersize or worn pins, soft parts, etc, can present problems when tuning triggers.

What I learned is small variations in pivot pin hole placement in the frame can of course change the optimum primary sear pin angle.

The blue prints I have seen indicate the primary sear pin angle to be 90 degrees to the pivot hole.

However to properly match the angle of the hammer notch, this sear primary angle is dressed to be 12-1/2 degrees from the 90 indicated on the prints to match up with the hammer notch at 90 degrees.

This makes the sear tip face parallel with the 90 degree notch at the hammer.
The 12-1/2 degree figure will vary slightly depending upon center to center frame variations and actual sear lengths.

As you know, it takes a rather strong magnification to see the true relationship at the sear pin tip to the hammer full cock notch.
Much more than a typical magnfying glass

This same magnification would be useful to determine if the hammer notch was deformed in any way.

This is my first post on this forum. However, I've been working with 1911's for many years. The blue prints available on the internet and in Kuhnhausen's book have been very informative.
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Old November 9, 2008, 02:43 AM   #4
Inspector3711
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I had a pull that changed on my Remy..as much as 2 lbs. from pull to pull. Maybe it doesn't relate but the trigger manufacturer told me that the only thing that can cause a trigger to change in normal circumstances is a bind between the action and the trigger group. I removed the group and babied it back in and it now holds the same pull weight. I thought he was nuts... I though I was careful... I'm a long time expert assembler...

He was correct.
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Old November 9, 2008, 03:20 PM   #5
Harry Bonar
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trigger

Sir;
You know, my frame was a little undersized and I had to dress the sear sides to get it to go in free, which I did.
I think it was hole misalignment, maybe a soft hammer or sear as Jim said.
The pistol is still at 5# now and I do carry it.
Harry B.
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Old November 9, 2008, 10:56 PM   #6
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Harry B,
Thanks for your response to an older post.
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