Glock 20 - Holding Open BEFORE Last Round

[Ugly Dwarf]

I recently came to own a G20. I've only had it to the range once, but I found the slide locking back with one round left in the magazine.

If I work the slide, it chambers the last round without issue. The slide locks open again after the last round is fired.

I've only run the gun with two factory 10 round magazines, but it seems to do this with both (1 - 100% of the time, 1 - ~50% of the time).

I've owned a few (and shot many) Glocks through the years and this is a new one for me.

Has anyone else seen this? Any thoughts on what might be causing this and/or solutions?

Thanks,

Dwarf

[Voo]

I would check the slide release... make sure it's been installed in the correct order. The bar spring that keeps it held down might be causing it to rise prematurely..

You might wanna try removing it and reinstalling it to make sure its correct

[Z ME FLY]

Make sure the rounds are fully seated in the mag. Some people bang it against a table to seat the rounds. I noticed this when I was shooting my friend's g20. For example if you have the bullet nose touching the front of the mag but a little space on the back where the brass and primer is, it will cause weird problems. Might be hard to explain but hope that helps.

[locosway]

250 rounds through my new G20 and no issues. I had one FTE but it was cheap ammo.

[Black Majik]

I'd concur with Voo.

Make sure the top pin is inserted first, then the slidestop along with the bottom pin. You'll want the slidestop spring to be underneath the top pin.

[Greg-Dawg]

Your thumb is riding underneath the slide stop.

[sammy]

Your thumb is riding underneath the slide stop.

Yep, this is what I was doing. If you shoot a 1911 on a regular basis a similar grip will cause that problem. To rule it out try shooting it one handed for a magazine. This tell you if you are having a problem.

[B Strong]

Your thumb is riding underneath the slide stop.

+1 - hand position is the first problem to look at with something that recoils as hard as the 10mm.

[locosway]

I don't know if it's just me, but I really don't notice the recoil. My .45 has way more recoil, but then again I'm only using 200gr at 1050fps.

[Timberland]

What kind of ammo, sometimes it can rattle around in the mag and trip the lock.

[Ugly Dwarf]

I would check the slide release... make sure it's been installed in the correct order. The bar spring that keeps it held down might be causing it to rise prematurely..

You might wanna try removing it and reinstalling it to make sure its correct

Good idea. This gun has an aftermarket slide release from the previous owner.

I'm told it's easy, but I'll need to locate some You Tube vid's on disassembly before I reinstall.

[Ugly Dwarf]

Your thumb is riding underneath the slide stop.

Thanks, I'll take a closer look at my ergonomics. Perhaps I'm holding this different because of the Crimson Trace grips and didn't notice.

On the other hand, this is the first time I've encountered this issue with any Glock (17, 18, 20, 21, 22, 23, 30 and 36) I've previously shot. Also, it's only on the last round that it holds open, not on rounds 1-9.

[Ugly Dwarf]

What kind of ammo, sometimes it can rattle around in the mag and trip the lock.

This was with 180 Gr. FMJ Double Tap's. I don't have any other variety of ammo to test with and haven't tooled up yet to roll my own 10mm on the Dillon.

[locosway]

The double taps are full power, I bet it's your thumb hitting the slide lock.