Glock 20 reassembly issue?

U

Uncle Malice

New member
I think most of you know that I know my way around Glock pistols. I've owned just about every model made at some point and have tested most of the available trigger jobs/mods, and many of the other aftermarket parts. This post isn't really about that, just reiterating that I'm comfortable with them and understand the internal engineering, etc.

I've noticed an issue on my Glock 20 Gen4, and it actually mirrors an issue that I had once with my Glock 29 Gen3 I had previously - at the time, I didn't realize the cause though.

After removing the slide from the frame, the striker should still be in that forward position with the firing pin block held in the upward position. If you lightly pull back on the striker lip, it will move rearward and allow the firing pin block to pop back in to place. This is normal functioning across all Glock models, but here is where things get weird.

If the striker is left in that forward position, the slide will go right back onto the frame with no issue. If the striker is moved to the rear enough for the firing pin block to pop up into position, the slide will lock up when trying to re-assemble the gun. The slide will move rearward to ALMOST the 'in battery' position and stop as if hitting a concrete wall. It simply will NOT move further rearward. There is no flexing of anything like it's getting caught on something - just a hard stop.

The slide can move back forward off the frame with absolutely no trouble. If you press down on the block and push the striker all the way forward, the slide will then pop right back onto the frame as normal. It seems to just be a minor design quirk of the 10mm, since both of mine have done the same thing. The thing that it bothering me is WHY. What is causing it to bind? The slide doesn't move up or down in any way whether the striker is 1/8" forward or rearward. What is binding up? For the life of me, I have not been able to figure what parts are binding up.

Anyone else that has a G29 or G20 have the same experience? This is 100% repeatable for me. I thought about sending an email to Glock just to find out why it does this. There is nothing wrong with gun though. It has been 100% flawless through over 1000 rounds of both 10mm and 40S&W(with conversion barrel). I love the gun... I've just never been able to figure out what it's doing here. My Glock 21 is almost identical and it does NOT do this. Weird.

Here's a pic for good measure. :)

(let me know if you need pics of what I'm referring to with the striker/firing pin block - it should be obvious)

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Put a small dab of light grease on the forward edge of the vertical projection of the trigger bar where the circle is in the picture.

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Normally, the striker is forward when reassembling the gun and that means that the firing pin safety is in the fire/fired position. It's being held upward by the firing pin which is forward and therefore won't let the firing pin safety move downward under spring pressure.

Since the firing pin safety is normally already in the up position when you reassemble the gun, the vertical projection of the trigger bar doesn't have to push it upwards during the reassembly process.

When you move the striker back, it allows the firing pin safety to drop down to the "safe" position. Now, when reassembling the gun, the forward edge of the vertical projection of the trigger bar has to push the firing pin safety upwards. Since it's not nicely ramped like the rear surface, it can take a good bit of force--especially if there's no lubrication at all.

Nice pistol, by the way. I haven't seen a Gen4 20 yet in person.
 

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Marvelous bit of information. The problem stated clearly, an answer and an explanation of the problem and a way to avoid the situation.

How am I going to remember this bit of info when I need it? I'll write post thanking the folks here at TFL for providing it and then it just may stick in my mind.
 
Thanks for the info John. I thought that might be it, it just seems odd that this only happens on the 10mm in my experience. I wonder if it's possible if I give firing pin block a little bit of a radius, if it will mitigate the issue. I'll give the grease method a try first, but it seems like a hard engagement.
 
For what it's worth my Gen4 20 does the exact same thing. Most of the time I just pull the trigger forward and it goes on, why I have no clue because it doesn't happen with my 3 other Gen4 Glocks (21, 23, 30), and they're all lubed properly.
 
I wonder if it's possible if I give firing pin block a little bit of a radius, if it will mitigate the issue.
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It will probably help, but the part is plated so anything other than just a light polish will likely go through the plating.

I haven't tried to do measurements to determine exactly what is different in the 10mm Glocks that would cause them to behave like this while the other calibers don't. Frankly, I think that the differences are small enough that they would be very hard to measure.

I know that Glock doesn't recommend lubricating the firing pin block or the vertical projection of the trigger bar, but I generally put a very tiny bit of light grease on the ramp on the vertical projection of the trigger bar and a similarly tiny bit on the firing pin block lower surface. It takes very little, and it's enough that neither of my G20s (a Gen 2 and a Gen 3) experience the issue you describe.
Most of the time I just pull the trigger forward and it goes on...
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That makes sense. If you look at the vertical projection of the trigger bar as you push the trigger to the forward position, you can see that it moves down slightly as the trigger goes forward. Apparently the small amount of downward movement is enough to insure that the two parts don't bind.
 
Yep, I can also confirm that moving the trigger forward works for me as well. It's not much an issue I guess, it's just an extra step to be aware of during reassembly.

The first time it happens I was racking my brain for the longest time trying ti figure out exactly what went wrong. I detail stripped and put it back together... and it worked. Figured I did something wrong and now it works. Took it back apart, and it did it again! :eek:

When I finally figured it out it made sense, but boy it sure was annoying at first.

As a side note, I got the Vickers Tactical slide stop in the mail for my G20 today. I usually use the Glock OEM extended, but figured I'd give this one a shot at the same price. I really like it so far. It looks and feels almost exactly like the slide stop on the M&P - which I also like - so that might be part of it. I'll take some pics and post a little review tomorrow, probably.
 
Thank you, thank you!!!

I know this thread is ancient, but I wanted to thank you guys. I got my first Glock last week, a G20 Gen4 and I was doing the initial cleaning and lube job on Saturday night. Then on the reassembly, I ran into this issue of not quite getting the slide back on. I thought I was gonna pull out what little hair I have left, but this thread saved the day! All of the details and comments got me back on the track and the slide, too! This should be pinned, thanks a million. :)
 
sorry to resurect this post,but last night I was getting my new 20 ready for some range time and had this happen.I thought I screwed something up and did an internet search and found this thread.LIFESAVER!!!!Thank you all for the help.(and now I found a new forum to hang in-LOL).
 
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