[BobRicks]

I have a Gen. 4 Glock 21 that I carry as a reserve deputy/detention officer for my job. I qualified with it about 4 months ago and it shot fine, and did not notice this problem then.

I dropped the mag out of it the other day to show it to my son, and when I went to reload it, the slide will not rack with a mag that is loaded with 13 rounds. I tried all three of the mags that came with it when I bought it. If you take out one round, and insert a mag loaded with 12 rounds, then you can rack the slide and put one in the chamber. If you try it with a mag loaded to capacity of 13 rounds, you cannot rack the slide.

Any ideas as to why this is happening?

 

[OMCHamlin]

Hmm, no, but I would suggest leaving your mags loaded for a couple of weeks and try again. My G30S needs the crush grip of Hercules to insert a fully loaded mag in with the slide forward. Obviously, with the slide locked open, it's not an issue.

 

[BobRicks]

Thanks for the reply. I leave them loaded with 13 rounds all the time and they have been loaded with 13 since I started carrying it back in November of last year. Don't have this issue with my G30s, just my 21. Like you said, with the slide closed, you have to jam it home to get the mag seated, with the slide back, no problem. Just curious as to what may be causing it.

 

[GRR]

Mags are tight to begin with. Load them up a few times and then leave them loaded. The springs will relax a little and you'll be able to rack the slide.

 

[vmann]

I had the same concern with my 27, I went to the range and it's a non issue...I lock the slide back, insert full mag, drop the slide and top off the mag...no issue, no worries

 

[F-111 John]

Serious suggestion: Load 13 in your carry magazine, and download your extra magazines to 12 rounds. If you cannot easily seat a 13 round magazine on a closed slide and confidently rack the slide, don't handicap yourself when you need it most. Use the 13 rounds to load your pistol, then holster it with 12+1. Your reloads will be 12 rounders, but if for whatever reason your slide doesn't lock back, you know you can drop the empty mag, seat a fresh magazine, and rack the slide.

 

[Butch]

I had the same concern with my 27, I went to the range and it's a non issue...I lock the slide back, insert full mag, drop the slide and top off the mag...no issue, no worries

Serious suggestion: Load 13 in your carry magazine, and download your extra magazines to 12 rounds. If you cannot easily seat a 13 round magazine on a closed slide and confidently rack the slide, don't handicap yourself when you need it most. Use the 13 rounds to load your pistol, then holster it with 12+1. Your reloads will be 12 rounders, but if for whatever reason your slide doesn't lock back, you know you can drop the empty mag, seat a fresh magazine, and rack the slide.

Good information above!

Any ideas as to why this is happening?

The shape of the slide's pick up rail (or some call it the stripper rail) requires that the rounds in the magazine be pushed down slightly when the slide is retracted.

The tightly loaded magazine makes it difficult to do so.

If you do as vmann says, take it to the range and test fire from that condition with your carry ammo to insure that it will be reliable for you.

I tend to do as F-111 John suggests, not only for functional reliability, but after carrying auto pistols most of my life I'm tired of dealing with that one loose round when unloading and loading, it's much simpler to just put it back in the mag.

 

[BobRicks]

F-111 John, and Butch. Thanks for the suggestions of downloading to 12 rounds. That is what I have been doing. Maybe I just need to get to the range and run a couple hundred rounds through this pistol and see if that will help. Hopefully it will work itself out after firing more rounds through it.

 

[GJHIII]

I had the same problem with my G23 Gen4, on the first range session. (With all 5 New magazines) So I only loaded and shot 12 rounds, for a total of 150 rds. On my 2nd range session all 5 magazines loaded, seated and chambered every time with 13 rds. Imho, Glock magazines need to be broken in like no other. Enjoy.

 

[ronin.45]

Good information above!


The shape of the slide's pick up rail (or some call it the stripper rail) requires that the rounds in the magazine be pushed down slightly when the slide is retracted.

The tightly loaded magazine makes it difficult to do so.

If you do as vmann says, take it to the range and test fire from that condition with your carry ammo to insure that it will be reliable for you.

I tend to do as F-111 John suggests, not only for functional reliability, but after carrying auto pistols most of my life I'm tired of dealing with that one loose round when unloading and loading, it's much simpler to just put it back in the mag.

This exactly. I've witnessed many guns that don't function 100% with the extra pressure of a full mag pushing up on the slide. Even if they do work, it is often difficult to seat a full mag on a closed slide. As Butch said, it is also a pain to deal with the extra round when unloading/loading. These are all the reasons I see no need to carry topped off.

 

[Photoman642]

Downloading by one is a fairly common practice. Much easier to operate the gun that way and probably easier on the mag spring.

 

[cciman]

I have this issue with my G30SF, and somewhat with G21. It continued after more than one year of ownership. I think there are variances on how tightly the slide fits on the rails, thus some guns do not have this problem.
2 solutions
1) Just live with -1 in the mag.

2)If that is psychologically unbearable to you (you feel you are not getting full ammo value from your gun) and you are willing to to take ownership of your actions, and since Glock is the ultimate owners DIY freedom gun : Here's what I observed:

I noticed that the G30 mag and the G21 mag both use the same listed model replacement mag spring, even though the mags are significantly different heights, and when you take them out the springs are the same length. Both springs are significantly longer than the mags themselves and still place adequate pressure (tight) against the last cartridge loaded. I cut off one complete 180 degree loop off the bottom of my G30 mag spring-- now it is much easier to load fully, and easy to rack the slide. No malfunctions.

 

[tom mac]

Springs will work in by flexing.... leaving compressed with 13 may help a little but not as quickly as flexing.
So just use them at 12rds as many times as you can and soon it will be fine with 13.

 

[JuneyBooney]

I had the same concern with my 27, I went to the range and it's a non issue...I lock the slide back, insert full mag, drop the slide and top off the mag...no issue, no worries

I have found that to be the case on many firearms brands. How you describe the remedy is the proper manner. But always make sure you drop the mag and then rack the slide when taking the gun off and placing it in a box etc to avoid a.d.

 

[G23G21]

Lock the slide back and insert a full mag and pull the slide back and release, then pull the mag out and stuff one more round in to top it off and stick it back in the gun. That way the round in the chamber will push the slide back for you. YMMV HTH

Just thought of something else... since most Glocks are kinda blocky up front, just stick a full mag in the gun and hold the front of the slide against a door jam or some other immovable object and push the gun forward. LOTS easier than trying to pull the slide back. Just something to think about if one hand is non-op.

 

[VCoupe376ci]

All .45ACP and I would assume 10mm Glocks are like this. My Non SF Gen3 G30 and my G30S both are tough to squeeze a full mag into with the slide closed and worse when you try to rack the slide. It will become easier as the mags wear in, but it will always be more difficult than it should be.

Also, leaving the springs under tension is not going to wear them out. Springs weaken as they go through compression and decompression cycles. Use of the mags is the only way they are going to become easier to load and use in the pistol when full.

 

[English]

F-111 John, and Butch. Thanks for the suggestions of downloading to 12 rounds. That is what I have been doing. Maybe I just need to get to the range and run a couple hundred rounds through this pistol and see if that will help. Hopefully it will work itself out after firing more rounds through it.

Steel springs exert force which is proportional to their change in length. So the extra force needed to load the 12th round is the same as the extra force to load the 11th or 13th round. So if we start at xlbs to load the 10th round we will need x plus y for the 11th, x plus 2y for the 12th and x plus 3y for the 13th. Obviously, just adding another y to the force is not going to make it so much harder to rack the slide at any point - what you are looking at, or experiencing, when racking with 13 rounds in the magazine is a step change which is not caused by the force in the spring and is therefore caused by something else.

The something else is the follower! With 13 rounds loaded the legs of the follower are so close to the bottom of the magazine that when it is loaded under the closed slide the stripper rail forces the legs of the follower against the base of the magazine. The consequence is that leaving your magazines loaded with 13 rounds will make no difference to your problem at all because all you are compressing is the spring and not the follower. If 13 rounds were compressing the follower on their own you would not be able to put the 13th round into the magazine!

The answer is to take the magazine to pieces and shave a little off the bottom of the follower's legs. Do a little at a time and try. Repeat until it works. Obviously, the legs of the follower provide it with a stable orientation. If you make them too short the follower will tend to tip and the magazine won't be reliable, but as it is, the followers are faulty and need to be modified or changed for ones with correct dimensions. Glock should send you new ones if you explain the problem to them as I have done above.

English

 

[4949shooter]

F-111 John, and Butch. Thanks for the suggestions of downloading to 12 rounds. That is what I have been doing. Maybe I just need to get to the range and run a couple hundred rounds through this pistol and see if that will help. Hopefully it will work itself out after firing more rounds through it.

Bingo....break them in with some range time. And have some fun while you are at it!

 

[Jakk]

I have found some Glocks are just like that with a fully loaded mag. For me it has been the small-framed guns (G27 & G29).

They never seemed to "work in" either. I keep them with a fully loaded mag, empty chamber. This gives maximum compression on the spring, but after a few years it is still really tight.

If I need to I can rack the slide back. But for typical loading, I just lock the slide back, insert mag, release the slide and holster it. It still goes bang.

 

[Glockdude1]

Use 2 magazines.

1 mag with13rds, another with 1 round.

Load the pistol with the 1 round mag remove mag.

Insert 13rd magazine. 13+1= 14