melissa5
03-14-2011, 09:03 PM
I found this on the Kahr forum on Glock Talk and wanted to see what ya'll thought about it.
"I recently bought a Kahr PM9, and in the first 100 rounds I had a nosedive every time I used the 7-round mag (the extended mag). I bought another extended mag, and had the same problem with that one. No problems with the 6-round mag (flush mag). So I stopped, and tried to figure out the problem. This is my story, and the fix I came up with for my gun. Your results may vary.
The nosedive is caused by what happens when one round gets chambered. That chambered round is dragging the next round forward in the mag a little bit. You can do this yourself by pushing one round out of a loaded mag, and seeing how the next round is dragged forward a little bit in the mag.
As that next round that was dragged foward rises up into position to be chambered, the nose catches under the feed ramp. There is a little gap between the top of the mag and the bottom of the feed ramp, and that's where the bullet's nose gets stuck. So the round never rises completely. Then the slide closes and jams the round in place, bullet still stuck under the feed ramp. You could hypothetically simulate this yourself, if it was safe to do so, so only use snap caps and not live rounds. Put in a half full mag (snap caps, not live rounds), with the slide locked open (Caution, keep the slide locked open). Push down with your finger (or a stick, if you are more careful) till you get the top round wiggling forward, and push down on it enough to get it stuck under the feed ramp. If you can do that, then your gun pretty much has a design flaw, or at least a little gap where a round can get stuck. I do NOT suggest closing the slide on a round you put into the stuck position.
Why do some mags work better than others? I've read that the 7 round mags are more likely to nosedive. The reason is the stiffer spring in them. A stiffer spring creates more pressure and friction making the rounds stick together. So a stiffer spring makes the top round more likely to drag the next round forward. But I think it could happen with any mag, given the right humidity.
Why does Kahr make a gun that allows this gap between the top of the mag and the bottom of the feed ramp? I don't know. With my PM9, I noticed that when the slide is locked back, I can push up on the muzzle of the barrel, to make the feed ramp lower even more, and close that gap up some. I think the gun might be designed to hopefully close that gap, but there's naturally some play. I found that the plastic of my frame was creating enough friction on the sides of the area under the barrel by the lug hole (the mass of steel block at the bottom of the barrel behind the feed ramp). Enough friction that normally the feed ramp wasn't lowering as much as gravity would otherwise have let it. Shooting the gun a bunch probably would eventually wear that plastic a bit, loosen things up, and the let the feed ramp drop more.
However, I believe that even if the feed ramp dropped all the way down (and I can force it down into that position with my finger), that there was still a little bit of a gap between the top of the mag and the bottom of the feed ramp. Furthermore, my feed ramp was overhanging the top of the mag by a little bit.
My solution was to not send it back to Kahr, because I doubted I could make them believe what the problem was (not sure why they let it happen in the first place). Instead I got Mr. Dremel out and ground the bottom of the feedramp back a little bit, then I polished it. Now the feed ramp no longer overhangs the top of the mag. Instead the two are more flush (vertically flush).
Secondly, to reduce the gap, I sanded the inside of the my plastic frame down, just the little area where it was binding the bottom of the barrel block. Just a little sanding off, then refitting, and so on. I only sanded about a finger tip sized area. When I was satisfied the feed ramp could more easily drop to the bottom of it's travel, then I cleaned it all up and put back together.
Note that with the orginal problem (as I see it), it is probable that some ammo would be more likely to be caught and nosedive than other ammo. If the bullet sticks out further, or is longer, then it's probably more likely to get caught under the feed ramp. This will vary by brand and type of rounds used. Also, some mags would be more likely to cause exessive friction and dragging of rounds, than other mags, depending upon the stiffness of the springs. And some specific PM9 guns might have more of a gap than others. And and there probably also some variance in how tight the plastic frame is, side to side, binding against the bottom block of the barrel, potentially keeping the feed ramp from dropping with gravity's help down as low as it otherwise could.
Before the fix, I had run 100 rounds before I diagnosed the problem. During those 100 rounds, my 6-round mag never had a nosedive. My 7-round mags always did, usually about the 3rd or 4th round.
After the fix, I ran another 100 rounds, and had 0 malfunctions. No nosedives, no problems of any kind. I also then ran 50 rounds of my defensive ammo, Speer Gold Dot 124gr HP. No malfuctions. Then I had my wife run 20 rounds (all 3 mags) of FMJ, no malfunctions of any kind. If she were to carry it, she would test the Gold Dots herself, too.
So, I offically declare the nosedive problem diagnosed and fixed. Kahr should owe me several thousand dollars for figuring it out for them But I'm not even going to contact them.
I really love the PM9. It is such a nice gun. So easy to carry, easy to shoot, very accurate, relatively low felt recoil, and now it works good to."
"I recently bought a Kahr PM9, and in the first 100 rounds I had a nosedive every time I used the 7-round mag (the extended mag). I bought another extended mag, and had the same problem with that one. No problems with the 6-round mag (flush mag). So I stopped, and tried to figure out the problem. This is my story, and the fix I came up with for my gun. Your results may vary.
The nosedive is caused by what happens when one round gets chambered. That chambered round is dragging the next round forward in the mag a little bit. You can do this yourself by pushing one round out of a loaded mag, and seeing how the next round is dragged forward a little bit in the mag.
As that next round that was dragged foward rises up into position to be chambered, the nose catches under the feed ramp. There is a little gap between the top of the mag and the bottom of the feed ramp, and that's where the bullet's nose gets stuck. So the round never rises completely. Then the slide closes and jams the round in place, bullet still stuck under the feed ramp. You could hypothetically simulate this yourself, if it was safe to do so, so only use snap caps and not live rounds. Put in a half full mag (snap caps, not live rounds), with the slide locked open (Caution, keep the slide locked open). Push down with your finger (or a stick, if you are more careful) till you get the top round wiggling forward, and push down on it enough to get it stuck under the feed ramp. If you can do that, then your gun pretty much has a design flaw, or at least a little gap where a round can get stuck. I do NOT suggest closing the slide on a round you put into the stuck position.
Why do some mags work better than others? I've read that the 7 round mags are more likely to nosedive. The reason is the stiffer spring in them. A stiffer spring creates more pressure and friction making the rounds stick together. So a stiffer spring makes the top round more likely to drag the next round forward. But I think it could happen with any mag, given the right humidity.
Why does Kahr make a gun that allows this gap between the top of the mag and the bottom of the feed ramp? I don't know. With my PM9, I noticed that when the slide is locked back, I can push up on the muzzle of the barrel, to make the feed ramp lower even more, and close that gap up some. I think the gun might be designed to hopefully close that gap, but there's naturally some play. I found that the plastic of my frame was creating enough friction on the sides of the area under the barrel by the lug hole (the mass of steel block at the bottom of the barrel behind the feed ramp). Enough friction that normally the feed ramp wasn't lowering as much as gravity would otherwise have let it. Shooting the gun a bunch probably would eventually wear that plastic a bit, loosen things up, and the let the feed ramp drop more.
However, I believe that even if the feed ramp dropped all the way down (and I can force it down into that position with my finger), that there was still a little bit of a gap between the top of the mag and the bottom of the feed ramp. Furthermore, my feed ramp was overhanging the top of the mag by a little bit.
My solution was to not send it back to Kahr, because I doubted I could make them believe what the problem was (not sure why they let it happen in the first place). Instead I got Mr. Dremel out and ground the bottom of the feedramp back a little bit, then I polished it. Now the feed ramp no longer overhangs the top of the mag. Instead the two are more flush (vertically flush).
Secondly, to reduce the gap, I sanded the inside of the my plastic frame down, just the little area where it was binding the bottom of the barrel block. Just a little sanding off, then refitting, and so on. I only sanded about a finger tip sized area. When I was satisfied the feed ramp could more easily drop to the bottom of it's travel, then I cleaned it all up and put back together.
Note that with the orginal problem (as I see it), it is probable that some ammo would be more likely to be caught and nosedive than other ammo. If the bullet sticks out further, or is longer, then it's probably more likely to get caught under the feed ramp. This will vary by brand and type of rounds used. Also, some mags would be more likely to cause exessive friction and dragging of rounds, than other mags, depending upon the stiffness of the springs. And some specific PM9 guns might have more of a gap than others. And and there probably also some variance in how tight the plastic frame is, side to side, binding against the bottom block of the barrel, potentially keeping the feed ramp from dropping with gravity's help down as low as it otherwise could.
Before the fix, I had run 100 rounds before I diagnosed the problem. During those 100 rounds, my 6-round mag never had a nosedive. My 7-round mags always did, usually about the 3rd or 4th round.
After the fix, I ran another 100 rounds, and had 0 malfunctions. No nosedives, no problems of any kind. I also then ran 50 rounds of my defensive ammo, Speer Gold Dot 124gr HP. No malfuctions. Then I had my wife run 20 rounds (all 3 mags) of FMJ, no malfunctions of any kind. If she were to carry it, she would test the Gold Dots herself, too.
So, I offically declare the nosedive problem diagnosed and fixed. Kahr should owe me several thousand dollars for figuring it out for them But I'm not even going to contact them.
I really love the PM9. It is such a nice gun. So easy to carry, easy to shoot, very accurate, relatively low felt recoil, and now it works good to."