Quoted:
Spring.  Once is too often.  Should never, absolutely never, happen half way down the stack.

One reason a Glock feeds 100% normally, is that the lump of the round pusher on the bottom of the slide where it goes between the magazine lips bounces and excites the stack of cartridges down into the magazine every time the slide cycles.  The spring is not strong enough, partially filled, to recover and push the rounds back up in time to feed.

Send to Glock.  Quite often they will replace the springs FOB.

Quoted:
Does longish term storage loaded cause this?

Quoted:
Geo:

In theory long term storage does not damage springs or weaken them.  It is a good theory if the metal and manufacture of the spring is perfect.  In the real world, sometimes things are not perfect.   A Glock spring should last about 5000 rounds of compression and expansion.  Fully loaded should not damage them.

In one of the 100,000 round tests years ago (Chuck Taylor???), Glock 17 magazines used to capacity and stored over and over eventually failed.  Loaded to 15 out of 17 rounds, they never failed.  

Two remedies to the unknown:
1)  download all magazines two rounds and never worry having avoided too much compression.
2)  buy a bunch of magazines, load the set of two or three you need up full, and rotate sets every few months along with the ammo having avoided too much repetition.

I think the better advice is to test every new magazine, use it separately for "real" or "practice", shoot it periodically, and fix or replace any that act funny.  Keep them dead dry inside so no lube craps up the tube and don't worry.

In any event, your "for real" magazines should never be used for practice after making sure they work.

Your practice magazines dropped, kicked, ejected, should never be reloaded "for real."

SPRINGS and DOWNLOADING and MAGAZINE ROTATION and AMMO ROTATION are nothing but an endless internet argument that is pointless other than in theory because no one else has YOUR magazines.

As I said, send the one (any from the same batch you can identify) back to Glock with an explanation the one fails to rise the stack at a certain point.

Glock magazines are a, if not the, main reason Glocks are so reliable.  They feed with a lot of up pressure on the stack and slide out of the feed lips straight into the chamber.  Doing it once says there is a problem with that magazine.  Gaston don't do random.

1997 FB1 tests:  3 Glock 23's, 3 Glock 22's, 20,000 rounds each, 2 total malfunctions.  

One malf a magazine is a 1911 problem.  One malf in a lifetime is a pissed off Glock owner using factory ammo in a cleaned gun shooting it normally.

Guns are cheap.  When you buy a gun, spend half that cost and buy spare magazines.  Spend the full amount for practice ammo.  By the time you shoot up the ammo testing the magazines, you will have learned how to shoot it.

(When I was working, switching from a 5-6 shot revolver to an auto pistol was such an increase of capacity, I never worried about short loading 15 to 13, 17-15, or whatever.  The P220 got stuffed full every time when it was carried.  Some of my 1990's magazines are catching up with use.  A set of three Glock 17 magazines bought at $75 each during the ban in 9mm for fun while I carried a .40S&W 22 have decided to let the last round pop out of the magazine when the second to last round is ejecting.  Lack of spring pressure holding the round under the lips.  Empty case and loaded round go flying.  That set of three have been shot about 15,000 rounds in a Glock 17 that had to be rebuilt of all small parts.)

Posted: Today 9:08:32 AM EST
[Last Edit: Today 11:12:14 AM EST by Fooboy]
Edited for snark.  Merry Christmas

LSA...i'm curious what do you do for a living?

Quoted:
Have you tried a different magazine?

Does it do it with other ammo in same magazine?

What follower does your magazine have?  How old is the magazine you have?

Quoted:



Gen 4, purchased in 2013.  This is not a consistent failure.  I don't believe it had ever happened.

the difficulty:  15 rounds of HST is about 10 bucks.  Running dozens of rounds through a mag to see if a $5 spring is to blame gets awkward.

I took the other two loaded mags and ran them no problem.

I see Wolff has plus 10 percent springs-- anyone tried them?

Quoted:
So let me get this straight... Your weapon malfunctioned one time and now its Glock imperfection.  

Pistols are mechanical devices, and regardless of manufacturer they can malfunction.

Your specific malfunction is probably the result of one of two things, either a weak magazine spring from extended use, or a round that was loaded with a out of spec OAL.

If you have never experienced this issue before I would not worry about it.  I would suggest numbering your magazines with a silver sharpie, that way if the problem continues you can diagnose if you have a magazine related issue.