Glock 21 reliability issues when suppressing

reynolds25 · Aug 30, 2018

Hello, I have a Glock 21 (gen 2 I think) and when I run it suppressed it is both accurate and quiet. About 25 percent of the time the slide does not lock back into battery after firing and must be pushed forward about an 1/8 of inch to lock back into battery, at that point the gun can be fired again. Can anyone help diagnose this issue. I have run 2 different cans (both of which have a nielsen device) on it and they both seem to have the same issue. Also I have the issue with many different types of ammo.

Since I have your attention are there any upgrades or tuning advice you all have for running glocks suppressed? I have a Gen 3 in 9mm as well with the factory threaded barrel so I will be messing around with that guy once I am able to fix the issues with the 21.

inkd · Aug 30, 2018

reynolds25 said:
Hello, I have a Glock 21 (gen 2 I think) and when I run it suppressed it is both accurate and quiet. About 25 percent of the time the slide does not lock back into battery after firing and must be pushed forward about an 1/8 of inch to lock back into battery, at that point the gun can be fired again. Can anyone help diagnose this issue. I have run 2 different cans (both of which have a nielsen device) on it and they both seem to have the same issue. Also I have the issue with many different types of ammo.

Since I have your attention are there any upgrades or tuning advice you all have for running glocks suppressed? I have a Gen 3 in 9mm as well with the factory threaded barrel so I will be messing around with that guy once I am able to fix the issues with the 21.

I have the same problem with my Glock 21. If I keep the Nielsen device heavily lubed, it helps some but doesn't make it 100% reliable.

I actually took it up to Engage Armament a while back and had them look at it, they were the ones who told me to keep it greased up. But, Andy also found something online that said people who were having this issue swapped to a higher power recoil spring and that seemed to solve the issue.

I've not tried this though, so I cannot reliably say it fixed the issue.

erwos · Aug 30, 2018

reynolds25 said:
Hello, I have a Glock 21 (gen 2 I think) and when I run it suppressed it is both accurate and quiet. About 25 percent of the time the slide does not lock back into battery after firing and must be pushed forward about an 1/8 of inch to lock back into battery, at that point the gun can be fired again.

This is your striker not pre-loading because your slide doesn't have enough energy left to overcome the striker spring and load the next round. You have a couple options to fix this:
1. Lighten the striker spring. Downside to this is potential light strikes if you go too far, at which point you'll need a lightened striker, too.
2. Increase the weight of the recoil spring. Obvious downside is that you now need to overcome this increased spring weight, and could have short-stroke issues.

Most people go with #1.

Glock 21 reliability issues when suppressing

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