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Discussion Starter · #1 ·
Have a Glock 17 Gen 3 that's about 1500 rounds old and noticed its starting to slam fire (slide locked back, new mag inserted, release and boom without trigger pull).

I found that sometimes when I pull the slide back and let it fly, the trigger pin sear misses (fails to engage) the trigger bar's firing pin sear. I can tell because when I do this without any round in the chamber, pulling on the trigger does nothing.

If I pull the slide back and let it come forward slowly or slower then it engages. I'm not sure if the trigger pin sear has become too short or the trigger bar's sear has become too short. Any ideas on how to fix this, I can't find any references to this problem online.
 

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It's hard to understand how this could happen without your finger on the pulled trigger. Modified Glocks sometimes get double fires, but that is happening as your finger has the trigger in the back position. Otherwise the FP safety would prevent this (I think?).

Maybe if the FP safety was defeated by a gunked up mechanism or dirty FP channel a slam fire could happen. Was the trigger reset when you released the slide, did you notice ? Glock don't have sears per se, there is just a lug on the FP assembly that engages the back of the trigger bar called the cruciform.

I could see if the connector did not raise the bar high enough on reset, that the lug could slip off, but again the I think the trigger would need to be in the back position for the gun to fire. The angle on the connector (from the top it angles to the right as you look) is critical to raise the trigger bar so the lug can engage it.

Sound like some modified parts here to be honest. Was it a new gun? They are not expensive parts to replace but right now you have a very unsafe gun on your hands.
 

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Sounds like you have stripped the slide and the firing pin safety spring is in sideways.
 

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You should detail strip, clean, and make sure that you have reinstalled all parts correctly.

See a qualified gun smith if needed. Good luck.
 

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The OP has made a couple of very unusual postings recently. I doubt that they describe anything real. Trolling it is, IMHO.

After all, how can any response be made to a post that cites a "trigger pin sear"?
 

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Discussion Starter · #8 ·
@Mike-M I've only been here a few days and wrote two posts. Sorry for the typo, I know my glock parts.

I found the problem, when the slide is pulled back all the way and allowed to fly forward, the firing pin sear doesn't catch the sear on the trigger bar. Something may have worn out.

Yes, I'm going to take it to an armorer.
 

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How do you know the 'sear' on the 'cruciform' isn't catching the 'firing pin sear' (usually referred to as firing pin lug)? You'd need a cut out on the rear, side of the slide to see it. I only ask 'cause you're using terms 99.9% of Glock people never use. If it's worn out, I doubt it got that way from shooting or dry firing. How many rounds on this gun?
 

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The OP has made a couple of very unusual postings recently. I doubt that they describe anything real. Trolling it is, IMHO.

After all, how can any response be made to a post that cites a "trigger pin sear"?
Something about Gen 4 slide going on a Gen 3 frame. I got lost when she referred to the slide as the 'upper frame'.
 

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Don't mess around with that. That's the kind of stuff that get's people killed.

Don't load the gun again until an expert has fixed it. (Experts are people who KNOW the problem, not people who ask questions on gun forums.)
 

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Have a Glock 17 Gen 3 that's about 1500 rounds old and noticed its starting to slam fire (slide locked back, new mag inserted, release and boom without trigger pull).

I found that sometimes when I pull the slide back and let it fly, the trigger pin sear misses (fails to engage) the trigger bar's firing pin sear. I can tell because when I do this without any round in the chamber, pulling on the trigger does nothing.

If I pull the slide back and let it come forward slowly or slower then it engages. I'm not sure if the trigger pin sear has become too short or the trigger bar's sear has become too short. Any ideas on how to fix this, I can't find any references to this problem online.
I think that in a case like this there are two options. If you are competent enough to completely disassemble the pistol, examine, clean, reinstall, replace defective parts. Do it.
If you are not, send it to Glock.
 

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I put some new parts on my g19, when I was doing my safeties/function check after reassembly it was doing the same thing. I took it back apart and found that the trigger spring was turned to the side wrapped around the trigger bar not in the notch and under tension so it would pull the trigger once it was racked.
 

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Discussion Starter · #15 ·
Decades with rifles, 3 months with a glock, so that's where the terminology is coming from.

I figured it was the firing pin lug (thank you Harold :) ) because field stripping it, I studied the function. If it does catch the cruciform there is (almost?) equal / negating spring tension on the trigger spring and firing pin spring so the trigger can't be pulled back.

If it does not catch, then lightly depressing the safety trigger thing in the middle of the spring (that one I don't know what it is called) will cause the trigger to go back without pulling on it. I observed this with the upper detached and when I think firing pin lug does not catch the cruciform.

When it does catch the trigger does not go back.

Again, I'm not 100% sure but this really does seem to be the case, I'm open to other possibilities. I already contacted glock and they want quite a bit of money to inspect and fix it.
 

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Was any trigger "work" ever done on the gun? Polishing, aftermarket parts.

Was the striker/spring changed, etc.?

Did you detail strip the gun (including the slide), before the problems started?
 

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As some have said, you're prolly at a point where an armorer should look at it. An experienced one should know straight away what the issue is.
 

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Discussion Starter · #19 ·
All OEM parts, it's a brand new pistol. The disconnector was polished, but not the trigger bar.

Slam fires did not happen until around 1500 rounds and no work was done around that time.
 

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This is an issue with Glocks. People get in the internet and start trying to mod them with out proper training. You may have accidentally bent something just enough to where after x amount of rounds it has jacked it up. If you are going to mod your Glock have somebody show you what not to do. There are certain parts or things you don't want to do. The statements you are making and how you are describing parts is telling me you don't know what your are doing and probably should not be taking apart your Glock any further than field stripping
 
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