Funny CZ-85 behavior, premature slide stop

[TheGloriousTachikoma]

At the range the other day shooting my pre-B CZ-85 for the first time. She digested the hollow points I buy just fine and two different FMJs (of course, what else do you expect from a CZ? ) However, something interesting happened. Using Mec-Gar 17 round mags, three out of four times, on the third to last round the slide stop activated itself. I'm shooting, and then suddenly the slide doesn't go back forward. I look in the ejection port and nothing looks jammed. I give the slide a little tug and she snaps back into battery and fires the remaining three rounds just fine, the slide locking back at empty. And this happened three times, the slide locked back on the third to last round.

Now, the way I hold pistols my thumb is nowhere near the slide stop on the left side and my trigger finger is down inside the trigger guard on the right (CZ85, ambi slide stop).

My theory is that the spring on the slide stop is a little weak and it's jumping up, but that the three times it happened it was all on the third-last round makes me think it may be the magazines.

 

[Walt Sherrill]

It COULD be a weak slide stop spring. Go to the CZ Forum and look for tips on how to tweak it. http://www.czfirearms.us/index.php?board=9.0

You should also look at the slide release, inside the frame, and see if you notice some marks on it -- from copper or lead rubbing against it. Rounds can nudge the slide stop if the stop is just a little out of spec. (I had that experience with my 85 Combat when I first got it...) If so, you may have to take just a little metal off of the slide stop where the nose of rounds rub when they are rocked forward during recoil.

Stronger mag springs from Wolff may also be a solution, as they can keep the rounds from moving around quite so easily... by pressing upwards with more force.

 

[chris in va]

Does it happen with the standard 15rd it was designed for?

 

[TheGloriousTachikoma]

The gun came with a CZ (Mec Gar) 16-rounder and it didn't do it with the 16, but I only spent two boxes of ammo through her and only used the 16 once. And no, it didn't happen with it.

 

[chris in va]

I'd just stick with the 16 MecGar then. It's what I used with my 75bd for years.

 

[1SOW]

The gun came with a CZ (Mec Gar) 16-rounder and it didn't do it with the 16, but I only spent two boxes of ammo through her and only used the 16 once. And no, it didn't happen with it.

The Mec-Gar 17 anti-friction mag follower is just a skosh different than the 16 rd factory/Mec-Gars. Walt Sherrill gave good advice. Check for signs of copper on the "NUB" of the slide stop. The newer ones are trimmed down a little to better pass 147gr and any bullets with longer straight wall showing.
Pics of the old style then newer:
https://lh6.googleusercontent.com/-...k%20of%20slide%20with%20heavier%20bullets.jpg

 

[JDGray]

There is plenty of slide stop area to engage the follower, I have had to remove some material on all but one CZ to keep this from happening.
As Walt said, look for copper on the nub, remove material if you see copper.

Installing a loaded magazine into the frame,(with the slide off, slide stop installed) you will see the issue.