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How to determine a worn/damaged sear?


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#1 jcwren

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Posted 03 July 2011 - 08:32 AM

I have an STI 2011 open gun that has recently developed an issue with the trigger "going hard" in the middle of a run. I'm told this can be a result of the over-travel screw being adjusted too far in. I've also read that this can cause damage to the sear. The problem is, I don't know what normal sear wear looks like. So I've taken some pictures of the sear and hammer through my microscope, and posted them on Flickr. Apparently because I'm "too new" (only been on the internet for 30 years, that should count for something), I can't post a link to the pictures, so burningsquirrels will follow up with the actual link.

Is this normal sear wear at ~5000 rounds?

Sorry about the quality of the pics. Had to hold the camera lens up to the microscope eye piece. I'd really like a trinocular head with a DSLR adapter :)

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#2 burningsquirrels

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Posted 03 July 2011 - 08:33 AM



jcwren's pic gallery.

Edited by burningsquirrels, 03 July 2011 - 08:34 AM.


#3 windscreen

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Posted 03 July 2011 - 10:35 AM

It is hard to tell on my smart phone, but the nose of the hammer hooks looks a bit rounded. That corner should be sharp.

The edge to inspect on the sear is opposite from the side pictured. You want to make sure the edges of the sear secondary angle are crisp, not rounded. Your picture does show, however, witness marks from the hammer half-cock notch. That is most likely from the hammer falling off the sear, following the slide, and getting caught at half-cock. This is what you probably experienced as the trigger going hard.

As for the overtravel adjustment, if you cock the hammer, hold it back with yor fingers, pull the trigger, and manually lower the hammer, you should not feel a bump as the half-cock notch passes the sear. If you can feel any tick of contact at all, the overtravel needs to be backed off.

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#4 logman

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Posted 03 July 2011 - 06:56 PM

This going hard could well be a disconnector issue with it not resetting as it should. Too little pre-travel could be a contributor.

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#5 jcwren

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Posted 03 July 2011 - 07:07 PM

I've added a couple more pictures to the set of the other side of the sear and the hammer hooks.

Edited by jcwren, 03 July 2011 - 07:08 PM.

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#6 burningsquirrels

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Posted 03 July 2011 - 07:20 PM

i have no idea what i'm looking at but that microscope contraption is pretty darn cool!

#7 shooter57

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Posted 03 July 2011 - 08:12 PM

your edges do look rounded. needs to have sharp edges.
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#8 Powder Finger

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Posted 04 July 2011 - 07:31 AM

Can't tell much from those, but You are probably right about having to LITTLE over travel as you can notice it hitting the half cock in the 2nd photo. At the least the OT screw should be adjusted to for sure clear the half cock. IMO most run the screw too tight I don't want the screw to touch the mag catch while shooting it just disturbs the gun too much.

#9 jcwren

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Posted 04 July 2011 - 03:29 PM

On the half-cock theory, I don't need to re-cock to fire again. I *think* releasing pressure on the trigger then pulling it again breaks the next shot, although it may be that sufficient pressure on the trigger is enough. It doesn't happen frequently enough where I can offer an exact description, and usually it's in the middle of stage where I'm more thinking about where I'm (in theory) aiming and moving.

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#10 burningsquirrels

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Posted 04 July 2011 - 03:38 PM

dude, you missed out on a ton of great food! we were wondering where you went LOL

back on topic. on SA guns sometimes the hammer spring is set pretty heavy and will still fire from half cock. mine did. :shrug:

#11 Powder Finger

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Posted 05 July 2011 - 07:11 AM

Not really saying it's stopping on 1/2 cock but that the marks in the middle of the sear indicate it's touching/hitting the 1/2 cock on the way down, which is caused by not having enough over travel, which can make the trigger hard and inconsitent.




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