G17 Gen4 Full Mag + Slide Locks Back

SNAFU84

SNAFU84

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I've been having a bit of an issue with my G17 Gen4 recently. Sometimes, the slide will lock back even when there is still ammo in the magazine. I've never had a failure to fire, feed or eject. The first time my slide locked back was after I installed an extended slide catch lever. I assumed at the time it was due to the way I was gripping the firearm and that the meat of my support thumb was forcing the slide lock lever up. So when I got home, I reinstalled the factory glock slide catch lever. It has happened with all my magazines, so I don't think it's a magazine issue. When I shoot, I have a very aggressive grip on it, so i'm not limp wristing it. Whenever it happens, I just bring the gun into my workspace, inspect the chamber and then I tap and rack and its good to go. Like I said earlier, i've never had any feeding, extracting or firing issues.

I've been using Winchester 115gr FMJ's. Basically, the first 100 rounds, I didn't have this problem. The next 100 rounds, I ran into the problem and then the next 100 rounds I didn't have the problem. It's kind of weird.


The envelope with the 2 spent casings that came with the pistol is dated 06-12-13. I bought it brand new and have put roughly 400-450 rounds through it. This problem has happened about 4 or 5 times. It's kind of annoying when you're shooting on a timed event. Has anyone had a similar problem like this before?
 
I had the same issue when I had the extended slide lock installed, as my aggressive-thumbs-forward-grip was activating it. However, the problem went away when I took it off. Do you have particularly long thumbs?
 
a couple of things

- grip is the first - if you are using the thumbs forward technique it will lead to this very easily if you are not bang on with your grip. One way to isolate the grip issue is to switch hand and shoot one handed to eliminate the variable for a few mags.
- 2nd issue is the slide stop lever. if you installed it you need to remember the correct sequence for the pin installs. You need to put the locking block pin in first then the slide stop lever followed by the trigger pin. If you put trigger pin in first then the locking block pin you will have defeated the slide stop lever spring. The easiest way to test this is to check that your slide stop has downward spring tension, if it flops around then you have it reversed.

Boltgun
 
Try if you see fit to fire it left handed.
If the problem stops, it was your right and thumb fondaling the slide release. Best way to eliminate user error.

My Sig 226 did this all the time. After years of firing glocks. Left handed I could never make it happen.

I was me, not the gun.

And or you have a slide release problem. Possible installed with the spring in a cranky position.

Just my thoughts.
 
Thanks guys.

silver - i haven't ruled out the option of calling glock. I have read that some of the Gen 4's had this issue due to a faulty guide rod assembly or what-have-you, but as far as I can tell from all the pictures and videos I have watched, I have the latest guide rod assembly.

WRH - not sure if my thumbs are mil-spec or commercial, lol. When I have my aggressive thumbs forward grip, my support thumb is able to reach roughly an inch past the take down latch. I do have big hands, but they aren't fat wish sausage fingers ( i mean no disrespect or offense by that comment, it's just an example)

8ball - i have a feeling this is my issue. i had the exact opposite problem when i was running my norinco np22. my thumbs would interfere with the slide catch and on an empty mag, the slide would cycle back into full battery because i would be depressing the slide catch

boltgun - next chance i get, i will test the one hand shooting. i only get to shoot during the ORA matches and don't have a membership anywhere yet, so it's a bit difficult for me to trouble shoot. as far as installation and re-installation of the new and old slide catch lever, it's all back together properly. when i take the slide off and push up on the slide catch and then let it go, there is an audible snap when it springs back into battery and there is quite a bit of force in it. i have a fairly strong feeling that it's my grip technique but i just wanted to see if anyone else had a similar issue. looks like i'll have to work on my grip some more. once the work season picks up, i should be able to get out to a range with a membership.

Again, thanks guys.
 
The meat of your support hand thumb is likely pushing up on the slide release lever. It's common with an aggressive thumbs forward grip. It's easy to identify if you take a close look when you establish your grip.

Grip technique needs to be adjusted to suit each individual shooter. There are some established best practices for gripping a pistol, but beyond that you may need to make slight changes to suit you. Small variations in your grip, finger placement, etc, can make huge differences in your performance and the reliability of your pistol.

You see people blindly following what they have seen in Magpul videos or the internet and they get so fixated with what they've seen from their flavor of the month SME without really understanding if that technique would work for them. You need to experiment and find out what works best for you. Professional training helps, because a good trainers can identify your issues and tweak you to get the most out of your limitations.
 
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Todd G from pistol training dot com had the the same issue with a g17g4 and he fixed it by replacing the slide release spring/lever.
 
Check the spring for the slide lock, I reinstalled mine and had the spring on the wrong side of the pin.

The result was that the spring pushed the slide lock towards the slide instead of away from it.

Caused it to lock open with ammo in the mag.

If the slide lock is lifted from the frame when you take the slide off then you reinstalled it wrong. Otherwise it's probably a grip thing like others have said.
 
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