Glock Mag Question

[lksmith]

Hey folks, been gone a while because of, well life ;)

Finally getting around to troubleshooting some of my projects from last year and have a question.
I have build several "glocks" from 80% lowers and pretty much all have performed except my "Glock 21" (45ACP Full size) and my Glock 23 (40S&W compact) on the 23 I'm pretty sure i just need to tune the springs since on 40S&W it locks back each shot with factory ammo, but fails to cycle with 9mm. The one that has me baffled though is the 21.
It has yet to cycle more than 2 rounds in a row, it feels/sounds like something is dragging but only thing I can see is the mag.
I have 2 SG mags and I think they are the problem. Anybody have tips on modifying mags to function?
Seems that while I have been living under a rock, gun stuff has gotten scarce and/or expensive!

Thoughts?

[45workhorse]

I can't help in modifying, but this place has the cheapest glock magazines.
https://www.cdnnsports.com/21-45-13rd-4th-gen-dual.html?___SID=U#.XzSl36eSnb0

[BK7saum]

I try to stick with factory magazines, I have seen numerous issues on the range with various malfunctions from non-OEM magazines. And yes, I know this is a "Glock", but an 80% lower/clone.

Also, most folks don't consider a magazine a disposable or consumable item. If you drop a mag in the feed lips and bend a lip,, or alter the width of the lips or change the presentation angle of the round, that magazine needs to be destroyed or at the very least,, marked and relegated to a range/practice magazine only.

Before I changed or altered anything, I would try an OEM/Glick mag, even though I know this is a 80% clone of a glock.

[BK7saum]

The mag may just be setting too high in the mag well and is dragging on the bottom of the slide. I would start with a new mag.

[FLINTNFIRE]

I find most magazine problems are from lack of cleaning , other then that springs need replaced if they have lost tension , most people try and shove every last round in a mag and manufactures put the maximum it is supposed to hold which is not what always fits without excessive pressure on spring .

If these are 80 % builds and you only have issues with your SG magazines find a glock magazine to try .

[Bigslug]

Glock mags are cheap enough I never saw a lot of sense in running aftermarkets.

I can't directly guide you on the .45's but have a lot of experience with the .40's. Those had A LOT of teething problems as the early guns and mags went from being barely modified 9mm's to incorporating more and more upgrades to deal with the increased slide velocity and battering the .40 dishes out. In the .40 platform, there was an increase in coils from the 9mm G17's 10 to the current G22's 11; there were five follower revisions that work with the early RH-only mag catch Gen 1-3 magazine bodies, and at least another 5 or 6 for the later Gen 3 / Gen 4.

But given that you're running a home-built, your issues may run deeper. Best solution is to play musical parts between yours and an OEM gun until the problem disappears.

[Petrol & Powder]

Glock mags have a small ledge or flat that limits how far the mag will travel into the magazine well of the pistol. There is a corresponding ledge in the mag well of the pistol that interfaces with that "stop" when the mag is fully inserted. Unlike a lot of other pistols, the floor plate on a Glock magazine is generally not the part that limits how far the mag will enter the mag well.

If you hold a factory Glock mag in you hand so that you're looking at the witness holes on the back of the magazine with the feed lips pointing up, you can find that "ledge" on the left side of the magazine, towards the rear of the mag body just below the feed lips. The corresponding stop in the mag well is located on the upper left side of the mag well, just under the ejector. If you remove the slide from the frame and place your finger down the left side of the mag well under the ejector, you can feel that stop where it is molded into the mag well.

The exact relationship of those two surfaces control how far the mag will go into the mag well. The magazine catch will prevent the magazine from falling out of the pistol but there is a little bit of tolerance in the depth at which the magazine catch will engage. (which is a good thing and it allows for some variation/dirt/wear/etc.)

The location of those critical surfaces that limit the magazine's depth in the mag well may be a bit of an issue with 80% frames and aftermarket mags.
From the OP's description, it sounds as if the mag may be too deep (far) in the mag well.

[Geezer in NH]

As a former dealer I blame the 80% Glock build.