Went to the range yesterday with family and tried to run a box of ammo thru my G19 and the slide kept locking back after every round fired. The mag was newer with Taran Tactical base plate, my slide stop is after market extended release that I has ran flawlessly for yeas. I only had one mag with me, but plan on going out today and trying all six that I have to narrow the problem. Only way I could get the slide to release was to use the slide release.

Anything else specific I need to look for while I’m at it?

When you installed the slide stop you probably didn't install the SSL spring on the correct side of the frame pin. Spring has to be on the BOTTOM of the small pin, not the top. Common mistake.

Am I a genius or what? Not really. I did the same thing installing a Vickers SSL on my G19. A friend had his Glock tool and we just reassembled it with the spring below the pin.

https://www.pewpewtactical.com...ed-slide-stop-lever/

https://www.code9evolutions.co...ed-slide-lock-glock/

The slide stop is a weak link. Thats the biggest thing addressed in the Gen 5's.

Yup. It a spring issue. Not mags.

For three pin Glocks, I created this little ditty to remind me:

The top pin is the locking block pin.
It's the first one out and the first one in.

Very important, otherwise, the slide lock spring has insufficient tension, and the pistol locks open after each shot.

I've also seen the slide stop lever spring break at roughly the point it rests on the pin and then it would pop over the pin and stick "up" with recoil. It's the only part I've ever broken on my Glocks.

If you want a replacement, I have a bag of them for the three pin gen 3/4 guns because I put extended slide stops in my guns. Email me and I will mail you one FREE.

Yeah I'd either say you're riding the slide stop with your off hand or the spring is over the top pin. Easy mistake and it should pop up very obviously when you remove the slide.

In my experience, riding the slide stop is an intermittent problem. I had this problem with a G34, and had to replace the stop with a non-extended version. If it happens with every shot it is probably the spring was not installed properly, as has already been pointed out. This was a problem I experienced with a used G23. Easily fixed.