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Thread: CW9 problem and the polymer myth

  1. #1
    Join Date
    May 2012
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    Default CW9 problem and the polymer myth

    My CW9 developed a problem where it would fail to return to battery. It would stop about 1/16" shy. Took a while to figure out what the problem was, in part because of that claim by Kahr that the slide only rides on the metal inserts and not the polymer.

    Turns out that's not true, at least on the CW9. There is a gap milled in the right rear corner of the slide. When the slide is moved back about 1/16" the insert is in that gap. At that point the insert is not holding the slide. The only thing keeping the pressure from a full mag pushing that corner of the slide up is the polymer rail.

    After a large number of rounds (less if your slide was as rough as mine) the poly rail will wear enough to allow the slide to rise when this gap passes and the metal insert gets caught in the gap. That's what is happening with mine. You can actually see the gap between the frame and slide get wider at that point.

    I sent this back to Kahr to have it repaired. They replaced the spring, the slide, and the barrel, but didn't fix this. Still does the same thing. The only difference was that I had to fire a number of rounds through it before it started doing it again.

    They refuse to acknowledge that this problem exists. They either really believe that "The slide does not ride on the polymer rails at all during cycling, only on the metal inserts both front and rear" or they are deliberately denying a known design flaw for fear of liability. Why they mill all the way into the slide rail slot I can't imagine.

    Please don't take it that I'm some kind of Kahr hater. I love my little gun and I will be getting it fixed one way or another. If not, I may pick up a K9 to replace it.

  2. #2
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    Jan 2012
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    Can't go wrong with a K9- the NYPD trade ins only cost a little more than a CW9. IMO you should get one while they're still available......Or if $$ isn't an issue, just buy a new one!

    As to the slide issue, can't comment on that. There are a lot of knowledgeable people on here qualified to discuss it though.....

  3. #3
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    Zenigata,
    Welcome to the forums.
    I think you bring up a valid point about the metal frame inserts. I wouldn't go as far as to call it a design flaw because of the failure of one particular pistol (yours is the first I've ever heard or read of having an issue because of this) or even to agree with your statement that "After a large number of rounds (less if your slide was as rough as mine) the poly rail will wear enough to allow the slide to rise when this gap passes and the metal insert gets caught in the gap." (that's supposition unless you've tested a large number of pistols and they did actually fail the same way), but, as your pistol has developed an issue, I do agree there is a chance other pistols could do like wise (especially out of spec guns). However, given the large number of poly Kahrs out there and the low (01) reported incidences of this happening (admittedly just on this board and a few others), I'd guess that in properly spec'd guns, the other three metal inserts are providing enough support/guide/bearing surface that the small amount of time the right rear rail is in the disconnector window has negligible effect/affect on the pistol (to include wear issues).
    Now with that said, I surely wouldn't mind seeing the metal rail insert made longer on that side of the frame so that it extends forward past the disconnector (BTW, that cut in the slide rail is there to accommodate the disconnector). Then again, I'd also like to see a metal insert or backing plate for the slide stop spring screw.
    Please keep us up to date on getting your pistol back on line.
    Regards,
    Greg

  4. #4
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    Sep 2009
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    67

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    the slide actualy does not ride on the polymer rails,, there is no strenght in poly rails for slide action in a semi. I can't think of one gun that rides on polymer rails,The back rails on the poly kahrs is what actually takes the brunt of the slide action and I have yet to see a worn out back rail or broken one even. Could it be longer as GB stated?? Probably so,, but darn kahr must have 200K of those poly guns out there and to my knowledge no issues with the about 1/2"" long back rails. They must indeed be long enought to keep the slide in perfect alighnment along with the front rails also being a guide to.... now like GB stated if the polymer rails are out of spec for some reason the slide will make contact but it is not by design. Normaly slide action wears these high spots down and all is well. the polymer rails are there to #1 strenghten the upper frame . #2 serves as a guide to properly reinstall the slide back on the frame. Those rails u could cut off with a knife and the gun will suffer no ill effects.

    Zenigate, sorry I disaree with ur analysis,
    Last edited by jocko; 05-13-2012 at 04:21 PM.
    . My PM9 has over 32,000+ rounds through it, and runs much better than an illegal trying to get across our border


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  5. #5
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    Speaking of my CW45 and CW9:
    Zenigata is correct in that for a small portion of the slide's travel it is not completely "captive" of the right rear, metal frame rail. To allow for function of the disconnector, the slide is machined in a way that a bottom portion of the right rail is missing near the rear of the slide. The slide may be "riding" on top of the frame rail when the open bottom portion passes by that rail, but it's not "captive" on that corner when it happens. Given the correct set of circumstances (possibly a gun that is out of spec in how the other rails fit) I find it conceivable that some vertical play could occur during that brief period when the open, bottom portion of the slide rail passes under the rear frame rail insert.

    Regards,
    Greg

  6. #6
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    Oct 2011
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    I have no desire to own a poly gun of any make. I realize they are for weight reduction especially in high round capacity guns for the consumer. For the manufacturer they are cheap to make. Plastic injected into a mold to save on weight or enhance profits. Titaniun or some other alloy that has to be machined costs more so the price of the gun would be higher to probably make less profit and not sell as many. What do companies choose nowadays?

  7. #7
    Join Date
    Sep 2009
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    67

    Default and thats

    Quote Originally Posted by kerby9mm View Post
    I have no desire to own a poly gun of any make. I realize they are for weight reduction especially in high round capacity guns for the consumer. For the manufacturer they are cheap to make. Plastic injected into a mold to save on weight or enhance profits. Titaniun or some other alloy that has to be machined costs more so the price of the gun would be higher to probably make less profit and not sell as many. What do companies choose nowadays?
    why kahr and some other makers still makie steel guns for guys like u that demand them. No doubt polymer is lowe rn price to make, but over all it is the extreme weight reduction that draws shooters to the gun. My Poly P9 shows zero wear anywhere, not a mark on my poolymer rails. Glocks have endured for years.Maybe someday there willbe a metal as light as polymer and affordable to make and machine and we will then see the rebirth ofthe steel guns. Wouldnot be a bad thing, for I amsure if a 14ounce PM9 polymer gun and a 14 ounce steel PM9 were i the showcase and priced the same the polymer would be sitting there a very long time. Who knows witrh todays technology and new materials, it could happen sooner than later to.

    How many here have MK series kahrs and state that although it is a super gun, it is heavy fr pocket carry, where as the PM/cm kahrs seem to do just well there.

    There will always be steel guns but i the lat half dozen years polymer models intordcutions far out number any steel introduction guns, except the 1911's still maintain their all steel over polymer and I think tha tis also becuase the shooting public wants the 1911's in stell over polymer. I love my K9, it is one hellof an atrtractive gun IMO, just not pocketable.
    . My PM9 has over 32,000+ rounds through it, and runs much better than an illegal trying to get across our border


    NRA PATRON MEMBER

  8. #8
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    Sep 2009
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    Default u both

    Quote Originally Posted by gb6491 View Post
    Speaking of my CW45 and CW9:
    Zenigata is correct in that for a small portion of the slide's travel it is not completely "captive" of the right rear, metal frame rail. To allow for function of the disconnector, the slide is machined in a way that a bottom portion of the right rail is missing near the rear of the slide. The slide may be "riding" on top of the frame rail when the open bottom portion passes by that rail, but it's not "captive" on that corner when it happens. Given the correct set of circumstances (possibly a gun that is out of spec in how the other rails fit) I find it conceivable that some vertical play could occur during that brief period when the open, bottom portion of the slide rail passes under the rear frame rail insert.

    Regards,
    Greg
    have a point although IMO with the 3 steel rails that is guiding the slide backwards, my opinion is that the polymer rail on the right side bears no force and could actualy be cut away with no loss of reliability. captive it is not. Not arguing, just giving my opinion.
    . My PM9 has over 32,000+ rounds through it, and runs much better than an illegal trying to get across our border


    NRA PATRON MEMBER

  9. #9
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    That must be another difference in the PM9. My PM9 doesn't ride on that part of the slide. It rides on the inset part just above those orange points in the pic, not the bottom of the frame sides. Thus, my rear supports never leave the slide.
    "Everything will be okay in the end. If it's not okay, it's not the end." - O. L.
    "We can't solve problems by using the same kind of thinking we used when we created them." - A. E.
    "The enemy of your enemy is your enemy's enemy. Period." - O.L.

  10. #10
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    Quote Originally Posted by OldLincoln View Post
    That must be another difference in the PM9. My PM9 doesn't ride on that part of the slide. It rides on the inset part just above those orange points in the pic, not the bottom of the frame sides. Thus, my rear supports never leave the slide.
    Old Lincoln,
    My apologies for not being clear in my previous post. The slides of my CW45 and CW9 do ride where you describe. Here's the photo again with a facsimile of the rear metal frame rail superimposed at several different positions along the slide rail. In two of the positions (A&C) the frame rail is captive between the top and bottom of the slide's rail (this limits vertical movement of the slide). In the other position (B) or any point between the two arrows, the metal frame rail has nothing below it to limit upward movement of the slide. As I said before, I don't think this would cause a problem in a properly spec'd/undamaged gun, but I can see where it could do so in an out of spec/damaged gun.

    Regards,
    Greg
    Last edited by gb6491; 05-15-2012 at 11:56 AM.

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