Transient P7 malfunction, insight needed

[YVK]

Posted the same on PCT.

I had a strange one today on the range with my P7M8.

First, I had a hell of a time trying to lock slide back without a magazine inside. No matter how hard I tried, I could only do it occasionally.

This wasn't the problem, though. The real one was this: several times when manually chambering a round, slide would get stuck in it's rearmost position. It wasn't a lock-back as squeezer wasn't engaged and squeezing it wouldn't release the slide. Tapping the slide would send it forward and chamber the round.

Otherwise, the pistol functioned normally.

This happened several times, but, when I got home, I wasn't able to reproduce it. On visual inspection, everything looks fine. The gun has always in perfect working condition and it was cleaned and oiled on 03/18/08.

I initially thought that, with my attempts to lock slide back manually, I managed to get slide stop assembly stuck in "up" position and slide kept catching on it. But, then, wouldn't pressing on squeezer release the slide? In my case it didn't.

Anybody has any insight?

[Riptide23]

I don't think you CAN lock the slide back without a mag in it. On many guns, the mag follower pushes up on the slide release to engage the slide notch, as the last round is ejected. Without an empty mag, there is nothing to push the slide release up into the notch, unless you do it manually, on a gun with an external slide release, like a USP.

The P7 does not have an external release, so you can't lock the slide back manually, AFAIK.

But I'm no P7 expert. Hell, I'm not much of an expert on anything...

Pat

[IRONMAN45693]

I just locked the slide of my P7M8 back with no mag inserted. The slide release is the sqweeze cocker, but there is also a slide lock just above the mag release on the left side of the gun. But, some of the other stuff sounds funny; couldn't tell you for sure. Did you just get this?

[YVK]

Riptide: you can lock the slide back on P7, with or without magazine in. Without the mag, you pull slide all the way back and then push in a little tab that's located, as Ironman said, above mag catch lever on left side. This raises slide lock assembly up and locks the slide.

Ironman: just had it for a first time time. I have over 7000 rounds through this gun, never had a malfunction except for one ammo-related annoyance.

I've taken it apart (slide and grips), looked all over, and everything looks fine. I now can lock slide back without any problem. I've tried to reproduce that damn thing with all my mags, 3 times with each, and I can't. I don't know if I should be glad that this appears to be a fluke, or worried that it happened and I can't get a clear answer.

I tend to think that I somehow got slide stop assembly in improper position, either by pushing on it too hard or, maybe, by installing grips incorrectly during last cleaning two days ago. I am still not sure how to explain that the gun would function normally in all aspects, except for slingshot chambering and manual slide lockback.

[AviatorDave]

The P7 does not have an external release, so you can't lock the slide back manually, AFAIK.

But I'm no P7 expert. Hell, I'm not much of an expert on anything...

Pat

Not trying to bust your balls as you were trying to help, but....

Statement 2 is redundant after reading statement 1. :)

The P7M8 slide lock is a recessed tab just behind the trigger guard on the left side, exactly as Ironman mentions.

And there is no reason I can see that could make any difference whether a mag is installed or not. When you push the slide lock tab, it's part of a long lever, the rear end of which pushes up in front of the bolt face, completely blocking it's forward motion.

There are two things I can see that could prevent it from working, 3 actually, but only two of them are likely -
First, if you got enough crud between the back part of the lever and the slide, or maybe behind the part of the lever that you push on, it could prevent it from going up far enough.

Next would be if the rear end of the lever were worn or broken off. There should be a flange about 1/4" long x 1/8" wide or so that extends to the centerline of the gun at the rear of the slide lock lever. Is it missing?

And lastly, and this is unlikely - the part of the bolt face where the lever contacts it could be severly worn. There is a ramped surface below it, but the part where the lever contacts is very flat.

To check yours, take the slide off. Push the locking tab and watch the lever move in the rear and check for worn shiny metal. Then look at the left side of the bolt face. If you can't find anything like crud or wear, put it back together and see if you can get it locked at all, and take a look inside the chamber, it's easy to see where the locking lever contacts the bolt face.

[Riptide23]

Not trying to bust your balls as you were trying to help, but....

Statement 2 is redundant after reading statement 1. :)

Ya know, the older I get, more more wise my grandmother was: "Better to remain quiet and have people THINK you're a fool, then open your mouth and remove all doubt."

I deserve busted balls... Thanks for reminding me about that button.

I'll shut up now, YVK.

Pat

[fullmann]

Posted the same on PCT.

I had a strange one today on the range with my P7M8.

The real one was this: several times when manually chambering a round, slide would get stuck in it's rearmost position. It wasn't a lock-back as squeezer wasn't engaged and squeezing it wouldn't release the slide. Tapping the slide would send it forward and chamber the round.

Otherwise, the pistol functioned normally.

Anybody has any insight?


I had the same problem with my psp once. even after cleaning it stuck open a couple times.

what the problem with mine ended up being is the gas system and piston assembly. apparently I didnt clean out the carbon build up good enough, and when the oil hit it, it expanded causing the tube that the piston goes into to effectively shrink in diameter.

think piston of 1/2" inch diameter moving in cylinder of 1/2" diameter that tightens to 31/64th"" at one end due to build up of filth, not enough of a diameter difference to fully lock it up, but enough to stick a little.

got after it with a carbon scraper and a good spritz of gun scrubber and it shoots like a dream again.

[AviatorDave]

I had the same problem with my psp once. even after cleaning it stuck open a couple times.

what the problem with mine ended up being is the gas system and piston assembly. apparently I didnt clean out the carbon build up good enough, and when the oil hit it, it expanded causing the tube that the piston goes into to effectively shrink in diameter.

think piston of 1/2" inch diameter moving in cylinder of 1/2" diameter that tightens to 31/64th"" at one end due to build up of filth, not enough of a diameter difference to fully lock it up, but enough to stick a little.

got after it with a carbon scraper and a good spritz of gun scrubber and it shoots like a dream again.

Ahh, I bet that's more likely to be the problem, because it would explain getting stuck in the open position (which I totally glossed over) and not releasing. If there was enough carbon build up, I can see how it might prevent the slide from even going back far enough for the slide lock to catch, so that when you squeeze the cocking lever, it can't release the slide because that's not what's holding it in place.

Any idea how long it had been since you used the scraper? The manual says 500 or 1000 rounds, or once or twice a year depending on whether you're reading the armorer's manual or the operators manual. I clean mine every time I shoot it, it doesn't take any extra time anyways.

[YVK]

fullmann: Thanks for input. I guess this does happen.
I thought of gas system fouling too, but I believe gas piston/cylinder are non-issue in my case. I have multiple reasons to believe that:

1. I use the same procedure (solvent - scraper - brush - Q-tips) every time I clean it. I clean every 200 rounds, unless I am doing a "non-cleaning trial" or training class. Last time I cleaned the pistol was 2 days ago, after completing a [carbine] class. The gun was clean when I shot it today, and the whole session was only 48 rounds; it didn't even get hot.

2. My cleaning routine has never changed since I bought this gun. If this were a maintenance issue, why would this happen after 7000 rounds?

3. The gun cycled perfectly otherwise (which is normally not a case with gunky cylinders), and slide went home fine in slidelock/squeeze cocker release reloads. It were only slide forward/slingshot reloads that caused it. When you had your gun do this, fullmann, do you remember how exactly the slide got stuck up: during cycling, with slingshot reloads, or at the lockback on empty magazine?

4. This gun has run flawlessly during 660 rounds non-cleaning trial I did 2-3 years ago. Same thing with 3 day class in January with 400+ rounds. Today was nothing volume-wise as compared to above or even my other practice sessions. My maintenance has not changed. The gun and piston were scraped and cleaned 2 days ago. This just doesn't make any sense...

I guess I am saying that, while I recognize that fouling of gas system is a theoretic possibility, I can't convince myself that was the case today.

[fullmann]

when my gun began to malfunction, it was almost like it was holding open on the last shot, but like your problem, squeezing it did not release the slide.

I did notice that it seemed 'sluggish' on the recoil, it almost felt like the roller delay rifles that we are so fond of. the sticking would also come and go, didnt seem to be any rhyme or reason as to when it would do it. I had multiple trips to the range without incident and without cleaning.

when I finally decided to see what was going on, I noticed that when I cycled the slide manually I could feel when it felt like it wanted to bind up. just a normal cycle didnt stick it, I had to pull back hard, almost like I felt like I was trying to break the slide off. then it would stick, almost every time, I guess it kind of explains why it wouldnt always stick with live ammo as I was using a known 'weak' and non-uniform ammo(wwb).

so I got to cleaning the gas system, I found that some of the carbon was really gummed in there, but only at the very bottom. I had to let it sit with penetrating oil overnite to get it to let go. even after the scraper and brush it seemed to still bind, after a couple days worth of letting it sit, and scrubbing it out it finally started to let go, and now, I'm happy to say it shoots beautifully.

I guess I learned a valuable lesson, gotta clean the p7 EVERYTIME I shoot it, and fully, not the quick over clean I was doing. I guess I got lazy after my tactical which seems to need absolutely no maintainance.

[AviatorDave]

YVK - you may have tried this already, but if you haven't -

Remove the slide, and take out the recoil spring. Put it back together and see if there's any binding anywhere along the slide range of motion.

It's not really a definitive test because I suppose is't possible to have no binding without the spring, but still have some drag with it, but it's one more thing to check.

[YVK]

Fullman, thanks for taking the time to answer.

Yep, your description (and very accurate one) is classic of fouled cylinder.

I still feel that my problem is different. Neither gun's behavior (normal cycling during fire and normal squeeze cocker reloads) nor my maintenance routine make chamber fouling likely in my case.

AviatorDave: I did look at the recoil spring, and I noticed that there is a slight, almost imperceptible curvature to it. I don't know if this is new, or it's been there all along. There is no binding anywhere, though.

I guess I'll have to see what happens during next live fire practice. I, on purpose, won't clean the chamber for now to see if I can reproduce the malfunction.

Thanks again to everybody who tried to help with advice.