I took my Glock 20 Gen 4 out a few months ago and was having the slide lock back with 1 round left in the mag again.

10 round Gen 4 mag with Wolff 10% springs and 10mm3 follower.

I have installed the 10mm4 follower with factory spring and will test that out next.

Quote from: chucky2 on October 22 2014 08:46:51 AM MDT

Quote from: PandaBear on October 14 2014 07:12:48 PM MDT
I called Glock today and they are sending me some 10mm4 followers. Maybe my slide won't lock back with 1 round still in the mag with these.

Be interested to see if you got yours.  I called to get 3 mailed to me and the guy asked me why I needed them, I told him to see if it would fix my Gen4 FTF issues.  He then asked me how many rounds I had through, I told him about 1500...he grudgingly took my serial number and said they'd send them out.  That was 3-4 weeks ago.  Another "win" for Glock Tech Support... 

I received them 3-5 days after I called Glock. Call and ask for technical support. Tell them you are having issues with your 10mm3 followers and would like some 10mm4 followers to see if they fix the issues.

I called Glock today and they are sending me some 10mm4 followers. Maybe my slide won't lock back with 1 round still in the mag with these.

This is the only ballistic gel test I could find on Youtube, but from the results it looks like bullet expansion and penetration would be more ideal with lower velocity.

I had the slide lock back with 1 round left in in the mag (10% Wolff Springs) on a few occasions last night with my Gen 4 and Underwood 165 TMJ.

I ran some 40 S&W right afterwards and had 0 issues. It's strictly a range gun, but I will likely give Glock a call to try and get some #4 followers.

Put 14 more rounds of UW 165 through my 15 to 10 round magazine and the slide locked back with 1 round left in the mag only 1 out of 7 mags. Seems as if my grip is to blame.

I'm thinking it's a combination of my grip, the flex in the frame, and the factory magazine spring not being strong enough.

The slide locked back with 1 round in the mag with the factory spring.
The slide didn't lock back with 1 round in the same mag with the Wolff 10% spring.
I only load 2 rounds into the mag each time.

The slide has never locked back with more than 1 round in the mag.
I shouldn't call it a FTF issue since the last round is barely being pushed forward out of the mag.

I'm considering getting an RMR installed on my Glock 20 Gen 4.

Since I will be running a Streamlight TLR, I think that the RM06 would be a better fit than the RM01 so I can adjust the brightness depending on the conditions.

Has anyone heard of anyone having any reliability issues running an RMR with hot loads?

I should be able to shower in Powder! Hope the situation gets better.

I just picked up a tub of this stuff at the gun range. Had to log on here to view this thread to make sure it would work for 10mm. Now that I have powder, I have a reason to order the rest of my reloading setup. Looking forward to hearing the results.

Update

Replaced the extended slide stop with the original slide stop and loaded 2-3 rounds per mag.

20 rounds UW 165 TMJ
2 rounds UW 150 JHP

Slide locked back with 1 round in the mag using factory 10 round mag with original spring.
I couldn't even tap, rack, bang because the gun thought the mag was completely empty.

Put the Wolff 10% spring in and had 0 issues.

I watched a video on youtube called "Biomechanics Of The Grip" and it taught me that I wasn't applying sideways pressure with my hands properly.

Further testing is required though...

You'd get more bang for you buck ordering some Underwood or PBR with shipping versus that 40 S&W powered stuff.

Reloading is the way to go, but powders are hard to come by right now. I don't know how long this shortage has been going on for as I just decided to start ordering reloading equipment last week just for 10mm.

The prices for Underwood 10mm are making me take the plunge into reloading. PBR is more expensive for me than Underwood with shipping, so I don't intend on buying from them. They would be my 2nd choice though.

I will likely buy SD ammo from Underwood, but that's about it.

Lots of people including myself have had problems with the 9mm 2183 followers which is why I decided to order a 10mm2 follower to try out. Might as well give it a try.

I have no smiles or bulges on any of my cases and cases eject as they should.

Glock 20 Gen 4 (Stock with extended slide release)

342 rounds total

289 Underwood 165 TMJ
35 Underwood 180 TMJ
13 Underwood 150 JHP
4 Underwood 135 JHP
1 PBR 200 XTP

Slide locks back with 1 round left in the mag over 95% of the time with 15 round, 10 round (with factory spring and Wolff 10%), and 15 blocked to 10 round mags all with 10mm3 followers.

Glockmeister 22lb Gen 4 RSA on the way and I ordered a 10mm2 follower as well.