Glock 20 Gen 4

[4949shooter]

Via the e-mails I've been trading with Glock, they use CCI Blazer for testing if you RMA back.  So the question to ask them is:  If I'm using in SAAMI spec ammo that is not mild, but rather, mid to high 10mm power, how are you going to do validation testing to test for FTF?

If they're going to just shoot a bunch of weak CCI Blazer and pronounce the pistol works fine, that's not going to help you (and shipping back to Glock is like $70, not cheap).

Chuck

True. If the gun works fine with CCI then Glock is not going to be of help. The next step is to try and tweak it on your own.

[10mm-Admirer]

I am new to 10mm. My Gen 3 G20sf's slide often locks back with one round left in the magazine too.  Even with brand new magazines.  Seems to do it most frequently with more powerful hot ammo. I shortened the OAL to 1.2500" on my warm book reloads and the problem has been reduced.

Timing must be an issue with Gock 10mms.  We expect them to flawlessly feed a wide variety of ammo of different velocities. Then we experiment with different weight recoil springs to reduce frame battering and stabilize velocities.  Slide velocity can be very fast with hot 10mm ammo.

We push boutique ammo producers to load to the highest velocity with heaviest bullets possible.

I have 20 hot boutique rounds  left then sticking to more reasonable book loads.  I don't want the wear and tear of the hottest loads for punching paper.

I'm not saying we shouldn't strive for a fully reliable pistol but realize that we are asking a lot of these pistols. I think we expect more from 10mm Glocks than any other caliber.

[The_Shadow]

Just a correction note, the

OAL you mentioned of 2.250"

should be 1.2500"

Yes taming the slide velocities is an issue to an extent.  The RSA of the Glock's are good to go to a point, but as you also mention the boutique ammo exceeds the setup.  Here is where competent handloading can provide quality rounds that are still effectively safe.

In the pull-down sections I have tried to show exactly what is being used by the various ammo makers, just to keep things in perspective.  I have often posed the question if these loads do in fact fit the SAAMI MAP specifications.   I would hope they do while being safely at the upper edge of this pressure value.

It would be nice to have Glock study this situation more in depth with the higher impulse ammo looking for what is causing so much malfunctions.  They should look at this not as a single unit but as a complete product model issue. 

[10mm-Admirer]

Yes, Shadow, I realized that measurement error and corrected it.  The longer erroneous measurement would definitely cause feeding problems for any 10mm!

I just don't expect my Glock 20SF to be 100% reliable with hot boutique loads.  Lots of power and slide velocity.

[10mm-Admirer]

I just shot 30 rounds of moderate book reloads in my G20SF and only had 1 FTF.  I think it was a fluke or related to the 22lb recoil spring.  I had no premature slide lock problems before empty.  I did have premature slide lock problems when shooting max book loads and boutique loads on a previous trip.

I noticed that even on my brand new Glock mags the first 3-5 rounds are pretty easy to insert.  If the upward pressure of the spring/follower is weak at the last few rounds, that could cause a feeding problem if the rounds couldn't be pushed up fast enough for the fast cycling slide.

[PandaBear]

I have a Wolff 10% mag spring that I will try next range trip. I had every intention of bringing it along last range trip, but forgot.

I've also had few instances where the last round did feed properly, but I'd say 98% of the time it doesn't.

Ordering a heavier spring may be the next step.

[10mm-Admirer]

Another thing I've noticed is the follower can be pushed down in the magazine tube and the front of the follower stick, jamming the follower down in the tube (not anti-tilt).

Seems like a magazine follower and spring redesign by Glock could improve the feeding reliability of the Glock 10mms.

[The_Shadow]

One thing I do, is disassemble my magazines to insure the springs are correctly installed.  I have found some that were backwards, this allowed the follower to tip down in the front...

[chucky2]

Interesting you note this 10mm-Admirer.  At the gun show where the Glock armorer worked on my Glock, he found 2 things mag related:

1.) Despite almost never (a literal handful of times) having more than 10 rounds in my 15 round mags, and never storing the mags loaded, my mag springs were 5-5.5" (I think 5", I'd have to go back and check my post to be sure) instead of the desired 6".

2.) He pushed down on the follower and there was some occasional hangups on them, a sticking like you noted.  It was strange enough that he went and found another 10mm mag he had to check if it was normal behavior.

So I do wonder if there are mag problems contributing to Gen4 issues...

[PandaBear]

Update

Tested a 15 round mag out of state with UW 165 TMJ with no success

Tried out the Wolff 10% spring in my 10 round mag today with little to no success

28 rounds UW 165 TMJ
4 rounds UW 135 Noslers
1 PBR 200 XTP

I might buy a new RSA, but if that doesn't fix it, then I give up.

I'm just going to have to sacrifice the last round in the mag.

[4949shooter]

Bummer.

[pacapcop]

Run EVERYTHING in stock. Take it from there. Outside that, grab a Gen 3. Ck MrGunsInGear on YouTube running 155 U/W in stock with a Gen 4. Might just have to shake the after market stuff. Just saying.

[PandaBear]

My Glock 20 Gen 4 is completely stock aside from the extended slide stop which is an OEM part. I'll put the original slide release back in and see what happens.

I have the exact same parts in mine as MrGunsNGear

I've tested it using

Factory 15 round mag
Factory 10 round mag
Factory 15 round mag blocked to 10 rounds
Factory 10 round mag with Wolff 10% spring

[4949shooter]

Refresh my memory...is the gun working with the low powered 10mm? CCI Blazer?

[PandaBear]

I haven't tried any of the lower powered ammo.

I've only tried
UW 165/180 TMJ
UW 150 Sierra JHP
UW 135 Nosler
PBR 200 XTP

Slide locks back with 1 round left in the mag. I ordered one of the Gen 4 22lb RSA's from Glockmeister. I'm wondering if the 10mm3 followers in the Gen 4 mags could be the problem. Does anyone know if the 10mm2 followers will work with the Gen 4 mags?