Glock 42 Slide Locking Prematurely

[Jlr2267]

Just bought a new G42 and tried it for the first time today. I had multiple premature slide locks. Each time, I could pull the slide back a bit and release and continue shooting.

Happened w/both mags and 2 types of ammo:

Winchester White box, 2 in 50 rounds
Speer Gold Dot, 12 in 25 rounds
100gr RN reloads, 0 in 100 rounds

Is this a known issue with fixes already implemented by Glock or am I dealing with a lemon?

 

[L-2]

This is a known issue with some success by those who have experienced the problem and having sent their guns back to Glock. Hopefully, yours isn't a "lemon".

Here's one of many threads on another forum.

 

[heyjoe]

is there a date on the fired cartridge envelope? i have one from august 2014 and have no problems. mine has a -1 on the magazine.

 

[Jlr2267]

Fired cartridge envelope dated 3/9/15. No dashes on the magazines

 

[JTQ]

Does it look like this, the first in the series? https://www.youtube.com/watch?v=Ka556--WF2o

 

[Jlr2267]

Does it look like this, the first in the series? https://www.youtube.com/watch?v=Ka556--WF2o

No, not at all. As I said in the OP, it is a "premature slide lock" meaning the slide is locking back with ammo still in the magazine.

After looking more closely, all mags are -02, frame is marked 2, slide lock is marked -1.

I can physically see that the Gold Dot ammo contacts the slide lock when I insert a mag (slide off) with 2 rounds. Slowly stripping off the 1st, when the 2nd comes up, the bullet ogive pushes the slide lock WTH?

 

[kokapelli]

Is it a new pistol or an early production?

There were problems with the early production pistols and then Glock made some changes.

 

[Jlr2267]

Is it a new pistol or an early production?

There were problems with the early production pistols and then Glock made some changes.

Fired cartridge envelope dated 3/9/15.

 

[Jlr2267]

I can engage the slide stop by pushing a cartridge with a "fat" bullet slightly forward in the magazine. Looks like the problem could be when a round moves forward in the mag under recoil, its ogive can engage the slide lock tab...I'd hate to start grinding on a new pistol, but unless there's a redesigned part, that looks like the only fix (or remove it completely)

 

[rcmodel]

I can physically see that the Gold Dot ammo contacts the slide lock when I insert a mag (slide off) with 2 rounds

Then it's an ammo problem more then a gun problem.

Or a gun problem more then an ammo problem, depending on how you look at it???

Easiest solution is to file of & polish the slide stop tab a frog hair so the bullets have room to miss it, but the mag follower doesn't.

It's pistol tuning 101 with 1911's and others.

Too many bullet shapes and seating lengths for one size fits everything anymore.

Rc

 

[Jlr2267]

Then it's an ammo problem more then a gun problem.

Or a gun problem more then an ammo problem, depending on how you look at it???

Easiest solution is to file of & polish the slide stop tab a frog hair so the bullets have room to miss it, but the mag follower doesn't.

It's pistol tuning 101 with 1911's and others.

Too many bullet shapes and seating lengths for one size fits everything anymore.

Rc

I keep a stash of 800 grit just for such occasions. I was hoping maybe Glock had an updated part, but looks like I've got the latest and greatest.

 

[heyjoe]

send it back

 

[WestKentucky]

Pull the part, check for any burrs or odd marks on your slide stop lever. Could be a bad stamping with a hunk-o-crud that got through assembly. I will pull my 42 apart tomorrow evening and measure it since I have no issues. Mine was bought straight off the UPS truck 2 weeks ago so it's mighty near the same vintage as yours....something that concerns me enough to pull mine and inspect it closely.

 

[Theohazard]

Just bought a new G42 and tried it for the first time today. I had multiple premature slide locks. Each time, I could pull the slide back a bit and release and continue shooting.

Any chance that your thumb is pressing up on the slide stop? I know early G42s had issues with the ammo doing this, but if the problem was the bullet pushing up on the slide stop, then you'd think that pulling back on the slide wouldn't release it.

It may very well be a problem with the gun, but 95% of the time that I've seen this happen it was because the shooter's thumb was accidentally pushing up on the slide stop. And that problem can be worse on a small gun like this one.

 

[Jlr2267]

Any chance that your thumb is pressing up on the slide stop? I know early G42s had issues with the ammo doing this, but if the problem was the bullet pushing up on the slide stop, then you'd think that pulling back on the slide wouldn't release it.

It may very well be a problem with the gun, but 95% of the time that I've seen this happen it was because the shooter's thumb was accidentally pushing up on the slide stop. And that problem can be worse on a small gun like this one.

That's a good point. I didn't think I was hitting it, but I just picked up the pistol with 2-handed grip and aimed and sure enough my right hand thumb knuckle is resting on the stop...I guess it's possible that with the snappier rounds my thumb is getting under the stop enough to raise it.

I will try some of the Gold Dots 1-handed tomorrow to see if that fixes the problem.

 

[Theohazard]

I will try some of the Gold Dots 1-handed tomorrow to see if that fixes the problem.

Awesome! I actually used to have the opposite problem; lots of guns wouldn't lock back on the last shot for me. The problem was me: My right (strong-hand) thumb rested on top of the slide stop on many of the guns I shot. Finally I adjusted my thumbs-forward grip so my right thumb was a little bit away from the frame and instead rested on top of my left thumb. That stopped the problem completely.

Even though you'll be shooting one-handed only, still make sure that your thumb stays away from the slide stop. On a small gun like this one it's still easy to push on the slide stop even when shooting one-handed.

 

[Jlr2267]

Glock 42: https://youtu.be/LskihWv3ALw

At about 14:20 mark he has the exact same issue I am having. He made sure his thumb was clear, slide still locked back...he pulled back a bit on the slide and it released.

 

[Theohazard]

Interesting. I wonder why pulling back on the slide stop releases the slide. That doesn't work when the follower locks the slide back. Maybe the recoil is moving the top round forward a little and it's catching on the slide stop tab, and pulling back on the slide stop releases the tension enough to allow the round to move back to where it's supposed to be.

Either way, it's still definitely worth it to rule out the possibility that it's your thumb.

 

[rskent]

Have you tried a bullet with a more tapered profile? Maybe a XTP. Gold dots are pretty fat.

 

[Jlr2267]

Have you tried a bullet with a more tapered profile? Maybe a XTP. Gold dots are pretty fat.

The Gold Dots are indeed fat, but looking at my 100gr RN ammo, it's even fatter!...and I had no problems with those at all. The GD are much hotter however. I'll try something with an XTP also.

 

[Jlr2267]

Back to the range today with disappointing results:

Tried shooting Gold Dots left handed and one handed, slide still locks prematurely. Changed my grip to hold my right thumb down with my left to be 100% sure I was not thumbing the lock...no difference, so I am now 100% confident it is something about the ammo.

Today's results:

Winchester Train & Defend JHP, slide locked 4 times in 12 rounds

Winchester PDX, slide locked 4 times in 6 rounds

Speer LE Gold Dots, slide locked 8 times in 12 rounds

Corbon 90gr JHP, trouble free 20 rounds

HPR 90gr JHP (xtp), trouble free 25 rounds

Pierce 100gr ball, multiple FTE but this was some crappy ammo and I could feel the inconsistent recoil...I do not recommend this ammo even for range practice

Herters 95gr ball, 50 rounds trouble free

Interesting that all the troublesome JHP were nickel plated, and all the trouble-free JHP were regular brass...coincidence?

I did notice that every time I had the premature slide lock, the round had slipped forward 1/4" in the magazine...pretty sure it is hitting the slide lock tab.

This process is getting very expensive & is bringing back nightmares of my Kahr CW380. I can't recommend the G42 to anyone not willing to burn a few hundred in ammo to find one that works.

This one is going back to Glock, then probably down the road.

 

[F-111 John]

To the OP: You have the -1 slide stop so that is the newest part. Others with problems identical to yours have squeezed the slide stop tab with pliers so that there is less side-to-side play of the slide stop lever without actually binding on the frame. It is a delicate process, but one that many have found to cure premature slide lock back.

You may also need to refine the shape of the slide stop follower tab slightly to increase the clearance between the bullet nose and the tab, without taking so much off as to lose empty magazine lock back.

If you look at the G42 magazine, it has a high lip on the front of the magazine to limit the forward creep of the top round, but as you discoverd if the rounds are pressed all the way forward in the magazine they can still snag the slide stop tab on their way up.

Some have gotten so frustrated with trying to solve the premature lock back issue that they have removed the follower tab altogether. You can still manually lock back the slide using the slide stop thumb tab, but lose the last shot lock back function.

 

[Jlr2267]

To the OP: You have the -1 slide stop so that is the newest part. Others with problems identical to yours have squeezed the slide stop tab with pliers so that there is less side-to-side play of the slide stop lever without actually binding on the frame. It is a delicate process, but one that many have found to cure premature slide lock back.

You may also need to refine the shape of the slide stop follower tab slightly to increase the clearance between the bullet nose and the tab, without taking so much off as to lose empty magazine lock back.

If you look at the G42 magazine, it has a high lip on the front of the magazine to limit the forward creep of the top round, but as you discoverd if the rounds are pressed all the way forward in the magazine they can still snag the slide stop tab on their way up.

Some have gotten so frustrated with trying to solve the premature lock back issue that they have removed the follower tab altogether. You can still manually lock back the slide using the slide stop thumb tab, but lose the last shot lock back function.

That's good info, thanks. I figured I had the latest parts, so sending it back probably would not help.

I will try what you've suggested and then try the Gold Dots once more (they seem to be worst case). If I can tune the slide stop to clear a GD in the forward most position, and still actuate on an empty mag, I think it would be good to go.

I did notice the stop has a lot of "slop" in side-to-side movement, which doesn't help matters, so I've crimped it a little.

I'll report the results. Really hope it works because I do like this pistol...very nice shooter when not locking up.

 

[rskent]

Jir3367

Interesting that all the troublesome JHP were nickel plated, and all the trouble-free JHP were regular brass...coincidence?

I did notice that every time I had the premature slide lock, the round had slipped forward 1/4" in the magazine...pretty sure it is hitting the slide lock tab.

Interesting and telling. The plated rounds are probably a bit slipperier letting them slide forward in recoil. This is where getting a solid grip comes into play.

Also, you might look to be sure that no lube has migrated into your mags. Its pretty easy to let a little lube got on a follower or feed lips. Then the mag wont
hold onto the round and lets it slide forward. Acts like the mag springs are shot.

Just thinking out loud.

 

[HoosierQ]

I have a Glock 21 that did just that. The slide stop spring was not installed correctly. Take it out and make sure the spring is installed correctly. I fixed my own problem.