Home > Glock Talk > General Glocking > Premature slide lock.

Premature slide lock.

  1. 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. I have to ask...

    How are you using a G19 magazine in your G17?
  3. Cut the grip down to accept G19 mags.

    Good eye though.

  4. Ahhh, gotcha. I would say to try it with your original ammo and see what happens. Sorry, probably not much help...
  5. 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.
  6. 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:


    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:

  7. 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. 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. 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. 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. 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. 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!
  13. 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. 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. Dont make me cut off my thumbs to spite my pistol...

    I will try this!
  16. 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. I will update after my next range trip :thumbsup:
  18. LoL good one!
  19. 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. Think about baseball.
  21. Took a while for me to accept it was the extended slide release on my g35.
    I actually changed my grip for a while until I decided that was silly and just changed the slide release. Problem solved. $10 part, 3 seconds to change.
  22. May I suggest having a second person shoot the gun to see if it occurs again.
  23. Sorry about that, I mis-read your original post.
  24. Yes, guns like yours are why I made sure to throw in a bunch of qualifiers in my rant, above.

    It DOES happen occasionally, but it's not very common at all.

    The thumbs being the problem is so common that it's almost considered normal.

    That's right, I said it; you ain't a REAL Glocker until you get premature lockback at least once! :supergrin:
  25. Only had this issue in Glocks with the 42, an issue that is now resolved. Officer's length Colts are another matter, and mine are the alloy framed Defenders. It happened repeatedly with the 9mm; part of the issue was a magazine that allowed the rounds to be too far to the left.
    Another fix is to drill a very small 'dimple' at the spot where the plunger sits when the slide stop is in the down position. It offers a little extra resistance to the slide stop engaging.
  26. I had this problem with a G42 that was definitely the nose of certain bullets bumping the edge of the slide stop. Inspecting from the top looked just like the OP's photos. Evidence of this was a brass film on the edge of the tab on the slide stop. (I could not determine if you had brass on the tab in the photo.) I filed down the area of the tab with the brass with immediate improvement. Eventually, I removed enough of the tab to solve the problem. G42 operated flawless after that. Just my experience
  27. Try shooting with one hand to completely not be able to touch at all. See what happens.
  28. Understood! And I didn't think you ranted, FWIW.

    Kinda like with Sig P series pistols people will often say, "My slide won't lock back after the last round. It's NOT my grip!"

    And 9 times out of 10... Yup, it's a right handed shooter, and it's his grip :)
  29. I had a pair of early G42's with the original no-dash slide stop, and neither of them could get through a single mag of any ammo, without the slide locking back with rounds still in the mag. Like you said, bullet noses were hitting the inner tab and bumping it up as if the mag was empty.

    Glock came out with the -1 slide stop and sometimes I could get through two whole mags without a premature lockback. I filed the inner tab and then squeezed the outer tab so the SS couldn't flop in-out so much. Between those mods, I was down to one premature lockback maybe every 500 rds. But the inner tab was just barely being activated by the follower on the last round, after some wear the follower started slipping past the inner tab.

    Glock finally came out with the -2 follower and it was better. When combined with the 03 mags, I haven't had a premature lockback for several thousand rounds now. Too bad it only took them two years to figure it out.
  30. Glad to hear I'm not the only one who has that problem with SIGs. :supergrin:
  31. Agree; that's entirely too slow.
  32. I didnt take it as a rant either.

    Been super busy. Have to get out to the range asap to try and get this figured out.
  33. In some small defense of Glock, the slide stop issue was so 'hit or miss' that it's not hard to imagine that they had trouble replicating the issue in Smyrna. My first 42, and those of two buddies, never displayed the slide stop issue. But it is the kind of crap that drives owners nuts.
  34. Very true.

    There are probably few things as frustrating for a factory troubleshooter as an intermittent stoppage in a small percentage of guns of a certain model.
  35. Got back out to the range today.
    Here was the procedure:

    -Shot her lefty, still had the slide randomly lock back. Did this with 2 mags before I again crossed out the problem being my grip.
    -Shot a box of the old Federal maroon box that I have put thousands of rounds through this glock with, Still got phantom lock backs.

    Threw in the OEM slide release, BINGO. Problem friggin GONE.

    So as I mentioned in the OP,

    So take note how the OEM slide release is moving with the slide off. Snapping back down nice and fast. So I take it out and put the Extended one back on. It seems to snap down just as fast and with the same amount of force as the new OEM one I put in that fixed the problem.

    At this point Im at a loss for what really is happening. all I know is I threw the new OEM one back in and my son and I shot a good 300 rounds through it without a hiccup.
  36. Glocks suffer more from after-market 'improvements' than any other pistol, IMHO. Simply because so many after-market parts are available, from so many manufacturers, being installed by owners with a wide range of skills and experience. Yes, they often work, and work very well...but sometimes they don't. It's really the 1st thing to consider if you are having problems. I have no idea what's happening with your Glock, or why, but you sure seemed to have solved the problem now that you've got the factory slide release back in the gun.

    Good job and good luck going forward!
  37. The "faulty" extended slide release was a glock brand part.
  38. Good troubleshooting on your part; a lot of folks simply won't "go back" to the old parts to confirm the new part is the problem.

    I've run into this kind of thing (add-on Glock-brand parts don't work reliably) a very few times, and I know it can be really frustrating. It's possible the part itself may be defective, or it might a be a simple tolerance stack issue with your particular pistol.

    Which reminds me; Glock actually makes a couple of different versions of this part. Are you sure you bought/received the correct part for your Generation/model? I think there should be a part number stamped on it, so it might pay to "look it up", just to make sure. I don't have the info on exactly which part number you need, but I'm sure someone here can come up with it.

    It's a Gen4 G17, right?
  39. After a bit of research, it looks like the part you need should be marked/stamped "7482-1" on the back of the part.

    (Glock Armorers, correct me if I'm wrong on this; I may not have the most up-to-date info).
  40. I had this same issue and noticed the same thing. The tip of mag catch being close to the bullet head. So I shaved the point from the mag catch down a little so give some more room. And so far it seemed fixed the problem. I'd give it a try.
  41. I had this happen to me the other day at the range. Been shooting glocks along time. Have extended mag release never had a problem. Then was shooting rapid fire and it started happening I was inadvertently hitting slide stop with my thumb. You are right 98% of the time that’s what it is.
  42. I stopped using extended slide stops long ago. A little filing of the surface that engages the notch in the slide with a jewelers file makes disengaging the stop easier.
  43. 98% of the time, statistics are made up 36% of the time, all the time....

    In all seriousness, the RMR came off this guy and it got thrown in the back of the safe. Same problem with new mags, new RSA and left hand shooting after 2 deep cleans.
  44. WOW 2016 Old thread, still not fixed??

    If happening when shooting with the left hand, less likely the thumb.

    Didn't read all, but the next thing to check is the slide release spring, make sure it is under the trigger pin, and not broken, or assembled incorrectly.
  45. I think he said he put the OEM slide stop lever back in and the problem went away. My first guess would have been since it's a chopped 17 to 19 grip, he's off a little on the chop...just enough for it to be unreliable.
  46. It started doing it again with factory OEM slide release.

    So to summarize, bought the G17 brand new and the first thing i did was put in glock extended slide release. Shot it thousands of rounds then out of nowhere, premature slide locks back.

    Throw in never used factory oem slide release, fixes problem for a very short time and then im back to slide release locking back prematurely.

    I have tried shooting it left hand for dozens of mags and my son has shot a few mags left hand and it acts the exact same way.

    The grip being cut too short makes no sense because by that logic a 33-round magazine would do the same thing.... You should be able to cut the grip all the way down (or up)to the bottom of the trigger guard and it still function 100% correct.

    Im about ready to scrap the frame, sell the slide and start with a fresh G17G5 because im completely out of ideas.

    Even if i did throw another brand new oem slide release onnit what is to say it is not going to start doing the same thing in a couple months just like the last one did?
  47. Are you planning to screw up that new G17 Gen5 as badly as you did the G17 Gen4? Was it worth it?
  48. Yes I am. With the 10k plus rounds through 10 different tactical pistol/rifle classes, it served me well while it lasted.

    Thanks for the reply!
  49. Mike, please, due respect, but what problem were you initially trying to solve?
  50. With chopping the grip?

    Tons of people do it. Its a common service offered by dozens of companies.