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Old March 26, 2011, 12:00 AM   #1
Alexander
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Problem with my Kahr PM9

On my last range trip the slide on my PM9 failed to lock back about 90% of the time with any mag. Kahr said my slide stop spring is probably out of spec and is mailing me a new one.

Here's the strange thing/problem: I had 6 stovepipes in 150 rounds but they all happened after I fired the last round in the mag. Can anyone explain that possible causal relationship? Why/how would a slide stop that's not locking the slide back cause FTE's?
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Old March 26, 2011, 12:05 AM   #2
JohnKSa
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Some handguns depend on upward pressure by the follower/remaining rounds in the magazine to aid the ejection process. I recall being told by one gunsmith/range owner that he had tested several guns from one well-known brand (not Kahr) and found that without magazines installed they would all dribble the empties down the magazine well when fired.

Since upward pressure from the magazine follower is also what causes the slide lock to hold the slide open on the last round there could be a connection.
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Old March 26, 2011, 12:50 AM   #3
Alexander
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Thanks for that info!

Now for another wrinkle: Can you think of any reason this didn't happen a single time with 75 WWB FMJ's fired but on 3 occasions during 50 rounds of PMC Bronze and on 3 occasions in just 25 rounds of Golden Saber?
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Old March 26, 2011, 01:56 AM   #4
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Just to be clear, I'm not saying that's what's happening, I'm just answering your question about what connection might exist between the circumstances you listed. It's a reasonable guess at what might be going on, but it's only a guess.

Following in that vein, I would speculate that there are some minor dimensional differences in the rims of the various types of ammunition you tested. It might be that there is some aspect of that particular pistol (either in the design or in some manufacturing variance) that makes it sensitive to the rim dimensions.

It would be a good example of why most experts recommend that gun-owners thoroughly test their firearms with the specific loadings they intend to use for self-defense. Sometimes very small differences in various types of ammunition can amount to the difference between reliable function and frequent malfunctions.
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Old March 26, 2011, 07:46 AM   #5
MW surveyor
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Try cleaning your mags first if you haven't done so. Could be some drag on the spring/follower.

Also, make sure that the slide is well lubed.

BTW - does this happen on the 6 or the 7 round mags?
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Old March 26, 2011, 09:07 AM   #6
MLeake
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May have no bearing at all...

... but I found with my PM9 that it did not function well with 7 round mags, but does just fine with 6 round mags.
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Old March 26, 2011, 02:54 PM   #7
Alexander
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Quote:
Try cleaning your mags first if you haven't done so. Could be some drag on the spring/follower.

Also, make sure that the slide is well lubed.

BTW - does this happen on the 6 or the 7 round mags?
I always clean my mags so that's not the problem. I know that Kahrs like to run a little wet so slide lube's not the problem either. Also, the problem happens with all of my 6 and 7 round mags.

I think Kahr is likely right about the slide stop spring. Last time I went out the slide failed to lock back 50-60% of the time. This time it was worse.

My main question was just why the FTE's were happening only on the last shot of the mags and why they happened with only certain ammo.
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Old March 26, 2011, 04:24 PM   #8
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Take a look at the INSIDE of the slide stop, the circular node directly behind and above of serrated outside thumb rest: it is the node which is inserted through the slide during re-assembly.

My P380 was having the same issues ( at @ 300 rnds.) and I noticed that node was pretty chewed-up. Asked Kahr for a replacement and got one but haven't shot with it yet. My PM9 slide stop also shows wear on the same spot but it locks back regularly and feeds/ejects perfectly; the wear is not as severe as on the P380.
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