Gock 21 locks slide back with certain ammo

O

Oleg Volk

Staff Alumnus
Shot USP45 and Glock 21 todat. With all kinds of ball and 185gr Silvertips, both worked fine. USP also worked fine with 230gr Gold Dots and Winchester JHPs. Glock 21 locked the slide back after firing either of those, about 30% of the time. It did so with both 13rd magazines. I had originally thought that the bullets hung up on the feeding ramp but later I realized that it must have been the slide licked back....dropping the slide with the lever brought the gun into battery.

Any ideas as to fixing the problem and what that problem is in the first place? Thanks.

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Oleg "cornered rat" Volk (JPFO,NRA)

http://dd-b.net/RKBA
 
This could be one of several problems.

when my agency transitioned to the G21 I experienced several stoppages like this which were caused by my thumb contacting the slide stop. Make sure that you are using a thumbs down hold during firing.

Another possibility is that your mags are defective. Glock recently re-designed the G21 mag (we're still waiting for ours). If this is a new pistol I would contact Glock and ensure that you have the new mags.
 
I am fairly sure that the ammo weight/energy level level is the culprit. I have fired some 200 rounds throughthat gun tonight w/o problems except with 230gr JHPs. My gun is old and came with two 13rd mags. It had identical problem with new 9-rd mag. I know I kept my hands away from the slide stop.
 
Oleg,

How about the slide stop's spring that keeps the slide stop pushed down? What may have happened is that if the spring's become weak, the slide stop's developed some up-and-down "play" to it. In other words, it's not held down firmly enough anymore.

What may be happening as a result then is when you shoot your gun, and it tilts backwards due to, of course, muzzle flips (21 does indeed recoil rather healthy), the spring doesn't have enough strength to keep the slide stop down with the rest of the gun. Hence, the slide stop "flies" upward and locks the slide in an open position.

Try to visualize this, then check the spring. Its weakness may not have been so obvious before.

If that's truly the case here, it's not much of a problem and can be easily fixed.

I really hope this will solve your bug.

Regards.
 
I do notice that after 120-150 rounds of .45, my arms develop a muscle twitch which makes it hard to aim or hold the gun firmly on recoil. Perhaps your guess about the slide stop is correct.

I also noticed that using the slide sto pto chamber the first round on the USP nudges the safety ON...potentially embarrasing or lethal. Ack!
 
185 grain Sierra JHP would not reliably cycle in my old G21. I think they were usually failures to feed...
 
CR,

While it is possible that a weak slide lock lever spring could cause this, it would also happen with other loads. If it is only happening with this one particular load, I would suspect your right thumb is the culprit. To test this hypothesis, shoot this load using your left hand. If the problem disappears, your thumb was the cause. If the problem persists, the slide lock lever spring is the likely culprit.

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Guns cause crime like spoons cause Rosie O'Donnell to be fat!

~David~

Remember, just because I'm paranoid,
doesn't mean they're not out to get me.
smileyshot2.gif


[This message has been edited by blades67 (edited February 06, 2000).]
 
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