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Discussion Starter #1
Hi all, new to the forum. Please see below. I am generally very concise, so please let me know if I need to include more info. If anyone has experienced a similar issue please advise.

Failure: Ammo in question is causing firearm in question to lock the slide to the rear prematurely, at varying magazine fullness.
Firearm in question: new P99c AS 9mm
Total round count: 268
Total failures from 115 gr Fiocchi FMJ: 0 / 136 total shot ("control group")
Total failures 124 gr +P Federal HST: 3 / 66 total shot
Total failures 147 gr Federal HST: 6 / 66 total shot

Two magazines were used to rule out magazine failures; failure occurred with both (both are Walther and came with firearm). I suppose they both could be duds.

I altered my grip to rule out the possibility that my thumb was pressing the slide release.

I visually inspected the ammo inside the mag, inside the frame, with the slide removed to try to rule out the ammo hitting the lever that locks the slide release on an empty mag. It does not appear that the ammo is hitting this lever, even after manipulating it to try to get it to do so.

Thanks in advance.
 

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My 99c eats HST like popcorn.


I did break it in with 400 rounds tough, all at the same session.


Did you clean and lube the pistol before firing it?
 

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Well, we can rule that out at least.
I'm out of ideas though. I have three, two full size and one "C" and I've never had any of them prematurely lock the slide back.


I'm sure someone else will be along with some more, and better, ideas for you.
 

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Discussion Starter #5
Well, we can rule that out at least.
I'm out of ideas though. I have three, two full size and one "C" and I've never had any of them prematurely lock the slide back.


I'm sure someone else will be along with some more, and better, ideas for you.
I appreciate the help either way.
 

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Never had that issue. 147 g HSTs are my carry rounds. I’ve never had one malfunction of any kind out of it going on four years and hundreds of rounds.
 

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I altered my grip to rule out the possibility that my thumb was pressing the slide release.

I visually inspected the ammo inside the mag, inside the frame, with the slide removed to try to rule out the ammo hitting the lever that locks the slide release on an empty mag. It does not appear that the ammo is hitting this lever, even after manipulating it to try to get it to do so.
If it isn't your thumb hitting the slide release, and it isn't the ammunition in the mag hitting the tab, then I'd suggest checking to see if the slide release spring is still there and it putting enough tension on the slide release. There have been reports of people bending the spring when running a rag down or up the magwell while cleaning the pistol.

It is curious that it is only happening on defensive ammunition, which tends to be loaded hotter. I would have guessed that it was your thumb, or the ammunition in the mag hitting the tab on the slide release. I would try some other ammo just to rule out the ammunition before I did anything else.
 

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Discussion Starter #8
Never had that issue. 147 g HSTs are my carry rounds. I’ve never had one malfunction of any kind out of it going on four years and hundreds of rounds.
They shot incredibly well out to 20 yds compared to the 124 +Ps in my P99c. I have never had this type of issue with the slide in any other firearm before. Once I get this resolved, they will certainly be my carry ammo.
 

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Discussion Starter #9
If it isn't your thumb hitting the slide release, and it isn't the ammunition in the mag hitting the tab, then I'd suggest checking to see if the slide release spring is still there and it putting enough tension on the slide release.


There have been reports of people bending the spring when running a rag down or up the magwell while cleaning the pistol.
Ok. Checked the spring after I got home from shooting. The spring is there, but I have no reference for how much pressure it is supposed to apply to the slide release.

I am a little biased in that I believe that spring is the issue. I could not think of any other cause.
 

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Hate for you to spend more money on defensive loads. But never had any issues with Horady Critical Duty or Defense. I hope you get resolve....most of the P99 plateforms have run flawlessly out of the box.
If no resolve, send her back to Walther. Good luck.
 

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Ok. Checked the spring after I got home from shooting. The spring is there, but I have no reference for how much pressure it is supposed to apply to the slide release.
The spring is basically just a thin piece of wire. I had one break on me, but it was after 6300+ rounds through the gun. With <300 through yours, there shouldn't be anything wrong with that spring unless you've been pushing up on the slide stop lever repeatedly with the slide off of the frame. (That's the only way I can think of to overstress that spring, because it's the only way you could move it outside of its designed travel range.)

I'd recommend giving Walther Arms a call - they'll most likely send you a shipping label.
 

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Discussion Starter #12 (Edited)
The spring is basically just a thin piece of wire. I had one break on me, but it was after 6300+ rounds through the gun. With <300 through yours, there shouldn't be anything wrong with that spring unless you've been pushing up on the slide stop lever repeatedly with the slide off of the frame. (That's the only way I can think of to overstress that spring, because it's the only way you could move it outside of its designed travel range.)

I'd recommend giving Walther Arms a call - they'll most likely send you a shipping label.
Thanks for the info. I have not manipulated the lever in that manner.

I am getting more curious about the typical clearance between the lever/tab that locks the slide to the rear on an empty mag and the ammunition feeding through the magazine. After more experimenting, I found that the ammo arranges itself when the next-to-shoot round is compressed by the underside of the slide such that rounds beneath it could contact that tab/lever. It is not dramatic but I could see where it may be enough to raise the slide release for an instant.

I had already contacted Walther and they are going to look at it, I was just hoping it might be something I overlooked. Hopefully it will not take too long for them to check it out.

ETA: clarification, spelling.
 

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I don't think you should rule out defensive rounds. The pistol simply shouldn't lock back early. With any rounds. If you are certain you have ruled out your grip being the problem. Is the small spring tasked with holding the stop arm down properly installed? It does not take a lot of push to lift the stop arm against the small spring nor does the arm have to move far. I can put a pull gauge on it if you like. The arm should move up and down freely but the spring should press down at all times until over-riden by the more powerful magazine spring acting through the follower.

Have you removed the slide, installed a magazine or two and made sure there is no contact between the mag body and the small inner tab on the arm. Perhaps your inner tab has become bent for some reason and is riding too close to the magazine. There cannot be any contact under recoil....bang the mag up and down after locking it in and see if movement can make it touch the inner tab. You will need a round in the mag to test this. No slide.

This just seems like it would be simple to diagnose. No, mine has never done this either. I'll put up some pictures of fitment in mine if it will help. 1917
 

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Discussion Starter #14
I don't think you should rule out defensive rounds. The pistol simply shouldn't lock back early. With any rounds. If you are certain you have ruled out your grip being the problem. Is the small spring tasked with holding the stop arm down properly installed? It does not take a lot of push to lift the stop arm against the small spring nor does the arm have to move far. I can put a pull gauge on it if you like. The arm should move up and down freely but the spring should press down at all times until over-riden by the more powerful magazine spring acting through the follower.

Have you removed the slide, installed a magazine or two and made sure there is no contact between the mag body and the small inner tab on the arm. Perhaps your inner tab has become bent for some reason and is riding too close to the magazine. There cannot be any contact under recoil....bang the mag up and down after locking it in and see if movement can make it touch the inner tab. You will need a round in the mag to test this. No slide.

This just seems like it would be simple to diagnose. No, mine has never done this either. I'll put up some pictures of fitment in mine if it will help. 1917
I agree, it should be simple to diagnose... but I cannot determine the reason between the spring being weak/installed incorrectly and the ammo hitting the mag release tab. I can assure you, it is not my grip, confirmed with many failures after tucking my thumb, shooting single handed, etc. The spring is indeed engaged on the release lever, and the lever remains in the down position at rest, although I cannot tell if the spring possesses the minimum necessary spring rate to resist heavy-loaded ammo recoil without measuring it (I do not have anything sensitive enough to measure the spring resistance). I believe the ammo can hit the tab on the mag release after experimenting with it, but it is not overly dramatic (nothing like what some owners of a certain CZ pistol have shown, for example). Perhaps someone could measure their mag release tab and I could compare? A rough comparison could be useful.
 

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I doubt it is the mags. If it is happening on both supplied mags, then the issue is probably somewhere else. Mag issues on the 9mm pistols are not just rare, but practically unheard of in the years I've owned my P99 and PPQ and spoken to others, as well as participated in this forum.

If you tucked your thumb and the issue still presented itself, then it probably isn't a grip issue either.

Try a different make/model of defensive ammunition and see if the issue persists. These pistols are not known for being picky in regards to ammunition to function correctly, but it would help with the diagnosis.
 

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For whatever it is worth....but first, Ima, can we get a picture of your thumb duck taped to the grip? :p Epoxy would be even better...! My pistol has never done this. I have two sets of Walther mags and they are different although marked Walther. The stock 10 round ones that came with the pistol and used for measurements and 14 round Italian made Walther banner 14 rounds with filler sleeve. Never an issue with either except for one of the extended ones having the spring in backwards when new.

Using a Lyman digital it takes 8 oz to pull the inner stop arm tab up to a point where the top of the thumb release is flush with the top of the polymer on the adjacent grip. It takes 10 to 11 oz to pull the stop arm up to the appx. position it would be in when fully engaging the the slide catch and it takes 1lb 4 oz to pull the stop arm almost as high as it will go before hitting the stop. I don't see that this additional movement damages the hold down spring in any way. It simply isn't that much extra reach.

The top of the follower on both mags has a significant slant to the right which will not allow rounds to stack against the left side of the magazine. My rounds are nowhere near the inner stop arm. This is not to say funny things can't happen under recoil where the follower might be compressed by the bouncing stack or rounds. Remember, it probably doesn't matter what the lower down stack of rounds are doing as they are nowhere near the stop arm engagement tab no matter how they are moving. It could only be the top or second to top round. My followers sit pretty snugly inside the mag body and without side to side movement.

With a fully inserted 10 round mag, the top, front, left edge sits



What my spring looks like and how it fits.



Rounds in the magazine sit well away from the inner tab on the stop arm. In this picture it looks like the top of the follower might interfere with the inner tab...it won't, it is just the angle of the camera. Shot from straight overhead the top of the follower won't touch the inner tab.

More later...got to get a design out. The only thing I can see is that the hold down spring it weak, broken or not installed properly. 1917
 

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Ha.....and I used a PPQ exploded view for my explanation. My bad....should have downloaded a P99C exploded view.

Well, duck taping the thumb to the grip wasn't all that bad. But when I used JB Weld, I lost a little skin during the removal process.

I also notice the same thing as you when inserting a loaded mag into a PPQ....seems to be plenty of room between the end of the 'nub' and the nose of a round in the mag. I really don't see any way for the rounds to move around enough to kiss the nub.

Its a mystery.

Send this pistol back to Walther with 2 or 3 boxes of the ammo you're using that's causing the problem. If they use ammo, other than what you're using, its not a valid test, PERIOD.

As always 1917....excellent photography. I can't get my little Brownie to do that. That's why I used the exploded view. Wrong one though.:mad:
 

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Those are I phone photos....didn't break out the real camera. Barbs you should have a close look at the hold down spring to make sure it isn't bent, dragging on the polymer anywhere or the trigger housing. When the stop arm is all the way down the spring should still be pressing tightly down on it. I can't remember the details of your earlier posts but if you are only having issues with heavier and more powerful loads....then I would say the spring is the problem all other things equal...like the JB Weld keeping your thumb in place. Some springs can be bent and more or less permanently hold their new shape....others won't. Since this is a self defense firearm...you might test slightly bending the spring down before sending it in. But, if you can't resolve it this is definitely a factory issue to resolve. If it were a .22 plinker...then we could play around with it a bit. 1917
 

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If you degrease the top of the stop arm, temp raise up the hold down spring a bit, place a small drop of JB Weld on top of the arm with the tip of a pencil or tooth pick....right under where the circular end sits you will be able to temporarily cause the spring to apply more downward pressure on the stop arm. The JB can be removed with no trace left and you would not have to bend the spring. JB sets up pretty quickly. Couple of hours and you can test. 1917
 
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