Sear spring adjustments question?

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Sear spring adjustments question?

Post by javaduke on 8/8/2016, 7:10 pm

I vaguely remember someone posting a link to a guide on how to adjust sear spring and which leaf to bend and to what level of tension. Let's say, I want to have a 3.5# pull - should I make the sear leaf as light as possible, as long as it still puts some pressure on a sear and prevents the gun from going full auto? Or should there be some ratio between left and middle parts? Say, 0.5# sear and the rest is trigger/disco leaf?

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Re: Sear spring adjustments question?

Post by cdrt on 8/8/2016, 7:22 pm

It's the one with the hook.  This is the thread you were looking for, I think.
http://www.bullseyeforum.net/t3935-sear-spring-question?highlight=sear+spring


Last edited by cdrt on 8/8/2016, 7:24 pm; edited 1 time in total
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Re: Sear spring adjustments question?

Post by Tim:H11 on 8/8/2016, 7:23 pm

I'm in the learning stages of this but I will say ( and Jon please correct me if I'm wrong ) that the majority of your trigger pull weight comes from how the sear and hammer are set up. How they are mated and how they are polished. There is a geometry that must be maintained so that you don't get full auto or run-away's. A lighter hammer spring may help some but it does not do a whole lot.

Your middle leaf of the sear spring holds the disconnector and trigger forward. If it is too light then you won't have a positive or quick reset after pulling the trigger. You could also have a problem that took me a little while to learn how to NOT cause. Hammer follow. And hammer follow could be caused from too light of the left leg of the sear spring that pushes on the sear. 

I would like to ask how heavy is your trigger now prior to any adjustment?
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Re: Sear spring adjustments question?

Post by javaduke on 8/8/2016, 8:43 pm

Well, right now it's right on the spot with 3.5# and medium roll. It used to be 6+ lbs and very gritty Smile 
I asked this question because unlike stoning and polishing the sear on a TR jig, the sear spring adjustment is pretty much 100% trial and error, so I was wondering if there's any preferred method to adjust the spring and check the tension as I go. There was a link to a page describing more "scientific" method somewhere, but I really can't remember what it was.

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Re: Sear spring adjustments question?

Post by dronning on 8/8/2016, 9:04 pm

javaduke wrote:I was wondering if there's any preferred method to adjust the spring and check the tension as I go. There was a link to a page describing more "scientific" method somewhere, but I really can't remember what it was.
You need a trigger pull gage:
For a 3 1/2 lb trigger pull you set the disconnector and sear springs to approx. 16oz each with hammer removed.  Remember the disconnector (middle leg) moves first and you want that to read 16oz before you engage the sear (left leg).  Once you have the disconnector leg set to 16oz. then you can continue the pull and engage the sear, set/bend the left leg until your gauge reads 32oz.  This puts 16oz on the sear because it is reading both legs (16+16).  This should give you a 3 1/2lb trigger, or very close.  When finished check with weights.

Full procedure is described in the link below
https://www.brownells.com/.aspx/lid=12535/GunTechdetail/2___lb__Trigger_Pull

- Dave
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Re: Sear spring adjustments question?

Post by Tim:H11 on 8/8/2016, 9:09 pm

Well I know that on brownells website there's a write up listed about how a smith achieves a 2.5# trigger pull on 1911's. He talks about having an empty frame with just the trigger, magazine release, and disconnector installed with the disconnector being retained by the sear pivot pin, and the sear spring being held in place with the mainspring housing. The write up lists checking the weight with a trigger pull scale to see how much it takes to move the disconnector alone and adjusting it to something. Then add the sear and test again adjusting until you have both legs at a combined weight of what it says you need. But there is a section in there on sear and hammer set up as well which is a big part of that. 

https://www.brownells.com/.aspx/lid=12535/GunTechdetail/2___lb__Trigger_Pull

I'm not saying try this. I'm just wondering if this is what might jog your memory. If your trigger is where you want it, or close then I'd just leave it. If it's close but not something you can deal with then usually just a minor bend one way or the other on the far left or sear leg of the sear spring should do it. And really with out a trigger pull gauge measuring it all out you just try and check and readjust.
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Re: Sear spring adjustments question?

Post by Tim:H11 on 8/8/2016, 9:11 pm

Oops... Looks like we had the same idea droning you were just faster on the keys!
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Re: Sear spring adjustments question?

Post by javaduke on 8/8/2016, 10:13 pm

Ah, yes, that's the one I was looking for, thanks, guys!

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Re: Sear spring adjustments question?

Post by DavidR on 8/9/2016, 9:59 am

On a 3.5# trigger you want  1.5# on the center leg, more than this is not good it creates extra drag on the slide from the disconnector then the balance on the sear, same for a 4#.  You can use a trigger weigh gauge to get it right.
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Re: Sear spring adjustments question?

Post by Bigtrout on 8/9/2016, 2:14 pm

Java, in my limited experience if you follow Jack Wiegand's 2 1/2 pound tutorial on Brownell's website for bending the disco and sear leafs while doing the proper measurements exactly to the script you shouldn't go wrong.  I only stoned the flat surfaces and left the angle surfaces alone as I have no fixtures.  Hint: Do an approximate mearsurement with calipers of the tip-to-tip distance from the grip safety tip before and after a bend,  That will give you a rough reference of how far you need to deflect the leaf.  

I did the procedure to my RO9 and it yielded a 48 oz. pull without reducing the stock mainspring, down from 5.5 lbs. There is an intrermittent slight creep but it was a constant slight creep before I did the procedure.  Good luck.


Last edited by Bigtrout on 8/9/2016, 2:19 pm; edited 1 time in total (Reason for editing : Accuracy)
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Re: Sear spring adjustments question?

Post by jglenn21 on 8/9/2016, 7:25 pm

I agree with Dronning on the 16/16 setup.. this is where I generally start for a 45 trigger.. the rest of the 3 1/2 lbs is your mainspring pressure(a tinny bit) and your sear / hammer..
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