So I just got done shooting my new G17. I was noticing that at times when the magazine finished the last round the slide would not lock open to indicate an empty gun. By 'at times' I mean that I could reload the magazine, shoot and then it would work and then do the same again and it would not. Is this because it is new and the the recoil spring needs to break in a bit???

I was shooting Winchester 9mm Luger 115gr FMJ.

Thanks guys!

Could be a problem with your bolt catch.

Maybe,inspect the slide lock/release

^^^^ Beat me to it.

Does it happen with all your magazines?

Yes= slide lock
No=magazine follower or magazine spring

This assumes that you have a good batch of factory ammo and did not change the recoil spring.

Make sure your finger isn't resting on the slide release, stopping it from going up.

Have a professional check it.

Bring the mags with you

I suggest sec or xring

Make sure your finger isn't resting on the slide release, stopping it from going up.

That's my first though, particularly with if you have the extended catch that comes with the Glock 34 or other models that get the catch further out.  I know with my thumbs forward and high on the gun, I occasionally encounter this.  Initially I thought it was ammo related since it never used to happen before I switched to the Federal white box 9 mm 115 gr FMJ.  I didn't think it was mag related as I tried tracking which mags.  In a recent pistol course, I didn't encounter it with a mix of Remington UMC and S&B 115 gr FMJ, so either my grip issue resolved itself or it was weak ammo. 

#1 - Shooter error is the most common intermittent failure of the slide to go into slide lock when empty.  Check your hand placement in regards to the slide stop.  This problem can be exacerbated by an extended slide stop lever.
#2 - Ammo.  Optimal is 124gr @1200 FPS.  Too light grain or light load.  Old ammo etc..

If 1 and 2 are resolved....

#3 - Magazine.  Be sure to label your mags and make note if the problem is related to a particular magazine or if the problem exists no matter the mag used.  As mentioned above if it is one magazine, mag problem.  If it happens on any mag, continue.....
#4 - Slide stop.  Possible incorrect install, or bad part.
#5 - Recoil spring.  If changed, go back to original or OEM. 

There are other possibilities but this is 99% of the issues.

#1 - Shooter error is the most common intermittent failure of the slide to go into slide lock when empty.  Check your hand placement in regards to the slide stop.  This problem can be exacerbated by an extended slide stop lever.
#2 - Ammo.  Optimal is 124gr @1200 FPS.  Too light grain or light load.  Old ammo etc..

If 1 and 2 are resolved....

#3 - Magazine.  Be sure to label your mags and make note if the problem is related to a particular magazine or if the problem exists no matter the mag used.  As mentioned above if it is one magazine, mag problem.  If it happens on any mag, continue.....
#4 - Slide stop.  Possible incorrect install, or bad part.
#5 - Recoil spring.  If changed, go back to original or OEM. 

There are other possibilities but this is 99% of the issues.

Thanks for all the insight. I think 'Surf' might have it right for me. I checked that my magazines were seating tightly against the slide stop, they were. There was no damage to any of my magazine followers. I put an empty magazine into the glock pulled the slide being careful to not touch the slide lock, it stays open. I did the same with a light touch on the slide lock and it won't open. I did this alternatively several times with each magazine and the same scenario happens each time. This leads me to believe that I am touching the slide lock when I am shooting causing it to NOT stay open after all cartridges are fired. I gotta work on that, I am new to shooting and to my G17 as well.


As far as the ammo goes, I will have to check that the next time I shoot. I have to get some 124gr or greater with a little hotter load maybe to see if that affects my problem. Still though at this point I think it really is point '#1' stated by Surf that is my problem. Shooter error