Glock 20 slamming shut after last round fired

[pinne65]

I have my G3 Glock 20 SF slam shut after the last round is fired sometimes. The first time it happened was after firing some semi hot 200 gr loads with the standard spring. I thought I needed a stronger spring. So I got a 20 lbs. But it kept slamming shut. The slide stop was also scuffed on the top. I got a new slide stop and the problem went away for a while. But it re-appeared. This time without me firing overly hot loads.

Has anyone else experienced this, have any thoughts what might cause it... Did I damage my gun permanently with the 200 gr hot loads that 1st time.

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[BlackSwanArms]

I've fired a lot of mix through mine and never experienced the slide failing to lock back, but I do not have 1000's of round through it. Are you referring to the magazine spring or guide rod spring? How are the magazines, tried any new ones? In the past on my other Glock's, with 10 of 1000's of rounds through them, when I've experienced this it's been from a week magazine spring.

 

[pinne65]

It's the guide rod spring that I upped to 20 lbs. I didn't know you could get stronger mag springs. I haven't fired that many rounds through the gun. 1500 at the most.

 

[mjbskwim]

It's the guide rod spring that I upped to 20 lbs. I didn't know you could get stronger mag springs. I haven't fired that many rounds through the gun. 1500 at the most.

I would guess that this is a magazine problem since it's the magazine that holds the slide open on the last shot

 

[bruzer]

I am only an internet expert but my first thought was mag springs too. Wolff makes magazine springs that are +10% extra power to improve feeding and magazine performance. At least that is what they claim from their website. I loaded them into my aftermarket korean 9mm glock mags and solved my issues with the slide failing to lock on the last round.
Make sure you use the stock recoil spring unless you are using HOT loads. If you have too strong of recoil spring and not enough power in the round it will fail to work the slide enough to lock after the last round.
Good luck and stay safe,
Mike

 

[Blitzkrieg]

+1 for Wolff gunsprings, I use them in all my serious arms from recoil springs to box mag springs and shotgun tube springs

 

[netcarrier]

Hi Pinne65,
I would take the Mag apart and pull the spring out longer Reassembly before buying a new one. The gun may need a good cleaning too.
Tony Portland, Oregon Area

 

[Blitzkrieg]

Hi Pinne65,
I would take the Mag apart and pull the spring out longer Reassembly before buying a new one. The gun may need a good cleaning too.
Tony Portland, Oregon Area

That is merely a temnporary fix if at all since if the spring is fatigued or weak it will eventually start causing the same issue

 

[netcarrier]

Hi Bltkrieg,
I know but now you kow that you need a new spring and thats whats wrong. Yes / No?
Tony Portland, Oregon Area

 

[bruzer]

While waiting for the new Wolff springs to show up in the mail, I stretched the stock springs in the aftermarket korean mags and IT DID NOT WORK. I am not a spring expert but once a spring looses its "spring" no amount of stretching will give it the proper spring back. You just end up with a longer weak spring.
Good luck and stay safe,
Mike

 

[netcarrier]

Hi bruzer "Mike",
Now that you have stretched the mag spring and it still will not lock the side back. Take the Side off put emply mag in the gun. Watch the side follower push up on the side stop. If it pushing the side stop up is it far enough to move the side stop to lock up the side? Watch were the mag follower hit the side stop.
Tony Portland, Oregon Area

 

[bruzer]

Manually moving the slide back the stretched spring would lock the slide back but the problem (no slide lock on last round) was still present when actually shooting. That is why I will still suggest getting a new magazine spring over stretching a spring.
Good luck and stay safe,
Mike

 

[jb11]

sounds like it might be short stroking.

 

[Blitzkrieg]

Hi Bltkrieg,
I know but now you kow that you need a new spring and thats whats wrong. Yes / No?
Tony Portland, Oregon Area

Buy the spring, man

 

[Mikej]

The after market mag for the wifes Kimber 9mm has a follower the goes a little cockeyed and doesn't quite engage the slidestop at times. A stronger spring may or may not help that situation. The mag does not appear to come apart though?

Mike

 

[pinne65]

I did buy one aftermarket magazine. And so far haven't paid attention which mag I have been using. But I will next time I go shooting.