Premature slide lock.

Discussion in 'General Glocking' started by MikeSantor, Sep 30, 2016.

  1. MikeSantor

    MikeSantor

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    Guys, what the hell am I missing?

    I have a pretty early gen 4 G17. I have shot thousands of rounds through it with zero problems. Only aftermarket parts are the extended slide lock that has been on since day 1, Ghost connector and extended mag release. It also has an RMR milled in it by Marc H.

    I was running a pistol 2 class a few weeks ago with a DIRTY gun. 1/3rd the way through the class I started getting premature slide lock backs. Here are all the variables.

    -Slide ultimately locked back with every one of my 9 G17 mags and 1 G19 mag.
    -Slide locked back with different number of bullets left every time but always *seemed to be towards the end of the mag (maybe last 7-1 rounds would be left in the mag when it would lock back.)
    -Even though my grip has never really changed, I diligently made sure my thumbs were not riding the slide stop
    -In the thousands of rounds shot, this is the first time I have ever tried a different kind of ammo when this problem started. It was PMC 115 Grain FMJ from SG Ammo. I ALWAYS use federal maroon box in the past. Could this possibly be an ammo problem? It is the ONLY thing I could think of that changed.
    -Slide stop spring IS under the top pin.
    -slide stop snaps back down nice and fast when lifted up and released (does not seem faulty in any way)




    So after the class I took it home and cleaned the hell out of it and just hoped it was due to the gun being hella dirty. Well I took it out again and sure as **** it is still doing it, with all 4 of the mags I brought out.

    I really dont think it is a faulty mag since it did it with all of them, it was a clean gun, it is put together correct, the lever and spring seem more then fine, im not riding it.

    literally the only thing I can think of is the different ammo. Like an idiot I didnt bring any federal with me. Only the PMC.

    What am I missing guys? what can I possibly be overlooking that is causing this problem?
     
  2. Jsferrazza

    Jsferrazza

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    I have to ask...

    How are you using a G19 magazine in your G17?
     

  3. MikeSantor

    MikeSantor

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    Cut the grip down to accept G19 mags.

    Good eye though.
     
  4. Jsferrazza

    Jsferrazza

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    Ahhh, gotcha. I would say to try it with your original ammo and see what happens. Sorry, probably not much help...
     
  5. Woodwrkr221

    Woodwrkr221

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    Most likely the PMC ammo has a bullet shape that's just different enough that the nose of the ammo in the mag bumps the slide stop while feeding. It could also be that the PMC ammo has a longer OAL that lets the same thing happen.

    With 1911's we gently file just enough off the slide release that there's just a knat's eyelash worth of space between the slide release and the nose of the ammo, no more but no less.

    With Glock's people don't seem to file their slide stops. Maybe they'll replace a slide stop but they don't seem to go to filling on them.
     
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  6. MikeSantor

    MikeSantor

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    I dont know about the ammo theory.

    Here is with the bullet seated all the way back in the mag. there is a TON of room to the slide stop:

    [​IMG]

    Here is one with the bullet seated pretty far forward. you can see the next round in the mag if you look close. And it is still super far away from the slide stop:

    [​IMG]
     
  7. PattonWasRight

    PattonWasRight

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    Maybe the pic, but it appears the outer tab of the slide lock is dog eared / bent away from the gun, you'd want it to be flush against the side. I guess the theory is that maybe your grip is drifting during rapid fire and you're pushing up the slide lock.
     
  8. MikeSantor

    MikeSantor

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    The tab as very flat/flush with the frame.

    I have done this repeatedly with a slow cadence of fire making sure my hands didnt ride up. Considering I have ran this glock in NUMEROUS classes and NEVER ONCE, not a single time had this problem, I just cant believe its my grip. I have got it to do it with my hands a half inch lower on the frame then I normally would grip the weapon.

    Nothing makes sense. The different ammo is the only thing I can think of that is different from any other times but that dosnt look like it is it.
     
  9. Woodwrkr221

    Woodwrkr221

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    Take an empty mag, load one cartridge and insert this mag into the frame.

    Push the cartridge down in the mag until the nose of the bullet is right beside the tab of the slide stop. Now lever the cartridge over to the left as far as it will go. Using a popsicle stick helps to lever the cartridge.

    Does the nose of the cartridge touch the slide stop? If it does there's your problem.
     
  10. PattonWasRight

    PattonWasRight

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    Woodwrkr ,... you're thinking the rounds are shifting to the side inside the mag as they come up? The ammo this is happening with is only 115 grains, so not a big fat bullet profile, but hey, it doesn't do it with other ammo.
     
  11. Woodwrkr221

    Woodwrkr221

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    You'd be surprised how they bang around in there.

    It's not the bullet weight but the bullet shape and OAL of the cartridge along with the dimensions of the particular slide stop.

    This is a common problem with 1911's that didn't get tuned by the manufacturer like they're supposed to and the fix is a few minutes with a small fine file.
     
  12. Jim

    Jim

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    Try shooting the gun left-handed, to ensure that you're not bumping the slide stop. Everything can bounce around more than you would expect during recoil.

    If that doesn't stop the problem, slide stops are cheap. I'd just install a new one and see what happens. If the problem still exists, you now have a spare for future use.

    Finally, try a real G17 mag to see if that makes any difference.

    And post back what you find!
    :thumbsup:
     
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  13. MikeSantor

    MikeSantor

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    Ok tried this. The bullet dosnt come anywhere close to the slide stop when pushed over as far as it can to the left (side of the slide stop.)

    What do you mean by "real G17 mag"? I tried 8 of them, all engraved and 1 G19 mag and got this to do it with all of them.


    Next range trip I will bring a new slide stop and a box of the federal that has ran like a champ in this gun. I will also try the left handed shooting theory to further prove its not my grip all of the sudden.

    Thanks for all the help guys. I wish there was something I was originally missing. Lets pray it is just the ammo. Or better yet just a slide stop considering I still have 700 rounds of that PMC. Although, that PMC ran like a champ through my gen 2 19...
     
  14. DJ Niner

    DJ Niner Staff Member Moderator

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    All I can tell you, is virtually every person who has complained about this with their Glock has said the same thing, and virtually every one of them was wrong. So, statistically, it's almost certainly your grip (thumb, or thumbs, actually).

    If you really want to figure out if it is your thumbs, here are some ways to check.

    - Shoot the pistol left-handed. If it doesn't lock back prematurely, it's probably not an ammo problem, or it would do it lefty, too.

    - At the range, set up a digital camera on a tripod on the left side of the pistol. Use a tall box, a divider wall at the indoor range, or SOMETHING to make sure the pistol is in sharp focus during firing (not focused on a wall or berm 20-100 feet away). Shoot several strings of fire (right-handed) until the camera has recorded several instances of the slide locking back prematurely. Then take the video clip and watch it on a computer or big-screen TV so you can see if your thumbs are moving around and getting anywhere near the slide stop lever.

    - Shoot the pistol right-handed, one-handed, with your thumb pointing straight up in the air, alongside the slide, like a bullseye shooter shooting a 1911 one-handed. If the thumb is completely off the frame and pointing upward, you won't be able to subconsciously move it on the frame to help minimize the recoil/muzzle-flip, and the pistol should function normally (no premature lockbacks). Combine this with the digital camera video option if you want, to prove to yourself that your thumbs are, or are NOT, the problem.

    I'll say it again: almost everyone who has this problem, is causing it with their thumbs.
     
  15. MikeSantor

    MikeSantor

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    Dont make me cut off my thumbs to spite my pistol...


    I will try this!
     
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  16. DJ Niner

    DJ Niner Staff Member Moderator

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    No matter how it turns out, post your eventual findings here, please.

    It helps everyone learn from others' actions, so sometimes we can avoid having the same problems; which means we are free to go forth and make brand new mistakes! :supergrin:
     
  17. MikeSantor

    MikeSantor

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    I will update after my next range trip :thumbsup:
     
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  18. PattonWasRight

    PattonWasRight

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    LoL good one!
     
  19. JoeyBones

    JoeyBones

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    I'm one of those few who had this problem and it legitimately was not my grip.

    HOWEVER, in my case it was in an old Gen 2 with the older, pointier slide stop tab... When firing hot SD ammo the rounds were jostling in the mag just enough to contact the tab that interfaces with the mag follower. Lighter recoiling range ammo wouldn't cause the premature slide lock. Replacing with a current production slide stop lever fixed it.

    I was told it was my grip too, and I (like you) was certain it was not, as I'd tested it thoroughly (as it sounds like you have).

    All of which is to say... I'm stumped. I'll be curious to hear how you correct it though.
     
  20. Stevekozak

    Stevekozak Stepping down to the gin palace

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    Think about baseball.
     
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