PM40 performance

[peashooter]

I put 100 rounds of WWB, and sixty FMJ reloads through my new PM40. The WWB was definitely hotter than my loads, but the gun still performed well enough with both. No real malfunctions except this small quirk.
The slide would not come foward when released on a full magazine. I had to bump it to get it to fall into battery. That also happened a couple of times with a less than full mag. Just a slight nudge on the rear of the slide was all it took to get it to fall into battery. These things happened early in the session, so I'm thinking it is loosening up already. I'll try some hollow points next time.

Snappy little bugger, but not objectionably so. Surprisingly easy to shoot fairly well. I can live with that trigger. It seems to shoot about 4 inches low at seven yards, but that could be my fault.

[CJCM9]

My CM9 had that same "catch" in the slide. http://www.kahrtalk.com/showthread.php?t=21494 Mine would only stick in that open position if I walked the slide, not that I would walk the slide with ammo in the gun.

The 4" low is probably a flinch OR, the Kahr sights are the kind that you need to hide your target behind the front sight. (as seen in sight image 3)
http://i70.photobucket.com/albums/i115/Gerdo_2006/sightimages_zps3566d2e3.jpg

[jocko]

IMO eliminate all3 photos and just go with POA, U willdo well, u won't shoot um in the same hole, but this gun is a prue defense gun, so IMO get good at 7 yards, get damn fast at 7 yards and having to concentrateon sights will slow u down. My betin a A SHTF situation ur never gonna see the sights,certainly u never gonna use more or less of that front sight either.

I guess my p[oint here is at least for this ol timer who doesnt see to fokkin wellin the first place is to train with your kahr the way u might someday have to use it to save ur life.

Pracrtice does not make perfect, but perfect practice does.. Just sayin

But saying that those 3 photos are IMO correct andif ur gerttinghighs or lows, one of those 3 will correct that. so I ain't knocking the photo or the message behind it. Nice photo job really.

[peashooter]

Another range session today. I fed it lots of good federal ammo. The round count is up over three hundred now, and it is still pulling the "nose dive" crap on me occasionally. And not just on the first round either. And with all three magazines.

What was a bigger disappointment was that I tried a magazine full of my normal SD ammo of choice, Hornady FTX, and it failed to feed the third round. The round went nose up and wouldn't chamber.

It's not inspiring much confidence as a bet-your-life-on carry gun.

[garyb]

Clean it and use a good gun grease on the slide and spring. Work the slide by hand several hundred times.
When I load my mags I make sure the bullets are well seated to the back of the mag by tapping the mag on my thigh before seating the loaded mag. Try that too.

If you have more than one mag, try them all.
I didn't have this problem with my PM. I did have the problem of it shooting low, left and that was definitely me. Shoot it off a bench to see if it is you or the gun. If it is the gun, simply contact Kahr and send it back for both issues to get them resolved ASAP. It MUST have your confidence as a bet your life on carry gun. It is that simple. But work with it by working the slide quite a bit and shooting another few hundred rounds to break her in good.... and clean/lube her good.
Most of all, be patient because it WILL get sorted out.

[scosgt]

Another range session today. I fed it lots of good federal ammo. The round count is up over three hundred now, and it is still pulling the "nose dive" crap on me occasionally. And not just on the first round either. And with all three magazines.

What was a bigger disappointment was that I tried a magazine full of my normal SD ammo of choice, Hornady FTX, and it failed to feed the third round. The round went nose up and wouldn't chamber.

It's not inspiring much confidence as a bet-your-life-on carry gun.

My CM 40 did the same thing. I was sure it was the gun. (talking about the nose dives). I bought one of those laser bore sighters. Sights are dead on.
I put the night sights on, and REALLY concentrated. It was the shooter. All will go in the bull if I do my part, but as a Glock shooter it is really easy to flinch on the long trigger pull.

Sorry, it is not the gun. Take it from me, I was fighting with people here over the low shots. It was me. Been shooting since 1971. It was me. The long trigger takes a lot of getting used to.

As far as the jam, polish the heck out of the feed ramp. It can only help. Make sure there is NO oil inside your mags, it allows the rounds to slide forward, which causes problems.

I have had NO problem at all with WW Bonded JHP 180 gr, although mine has fed all JHPs I have tried. It can be sensitive to bullet length and shape, since the round basically bounces off the ramp into the chamber. Try a few different carry loads, most will feed perfectly. The Hornady may be a little too sharp of an angle for the little gun.

[jocko]

in the propper prepping thread there is discussion on how to check to see if by chance that rounds (bullet) is hittingon the inside of the slide release lever. The bullet shold pass by close but never touch that inside of the lever or ur gonna get a miss feed. Easy to check out, If it is hitting, email kahr state ur problem and they will send u a new slide lock lever and then in the meantime u can slightly modifyt where that lever on the inside is hitting the bullets. Just some fine sanding sometimes takes care of that issue.

[peashooter]

After a lot of studying, research, and comparison, I have determined that Kahr 40 S&W semi-auto magazines do not operate like every other 40 S&W semi-auto magazine I have looked at. Every 40 S&W semi-auto magazine out there holds all the rounds parallel to each other... except the Kahr. When Kahr mags are loaded full or near full, the rounds underneath the top round are pointed down. This is obvious if you look at the front of the exposed rounds.

Normally, when the slide moves forward, it contacts the upper exposed rear edge of the top round, and pushes forward. As long as the round underneath the top round is parallel with the top round, the top round can smoothly be stripped from the magazine in a normal manner with no excessive friction or catching points. The Kahr magazine is not like this.

On a Kahr 40 magazine, when the slide moves forward, it contacts the upper exposed rear edge of the top round, and pushes forward. Because the underlying round is pointed down, its upper rear edge catches in the extraction groove of the top round. This accounts for the resistance of the slide to move further forward. It also creates a moment, or leverage, on the top round, forcing the front of the round down, and you have the "nose dive."

What is causing this is a loose fit, and excessive flex, of the magazine follower. It cants forward under the higher spring pressure of a loaded magazine, allowing all the rounds except the top round to also cant forward in a nose down position.

To prove this, I temporarily glued a small piece of plastic to the lower rear corner of the magazine follower to improve its fit and resistance to this movement. This greatly reduced the nose down position of the lower rounds, and eliminated the catch in the slide, and the round "nose dive". The flex in the follower still allows some mis-positioning of the lower rounds when the magazine is full, and I suspect that this fix would likely eventually simply cause the follower to break.

BTW, I have confirmed these facts on all three magazines that came with the gun.

Yes, there are many many Kahr pistols out there where this magazine follower flex and fit does not cause problems. In all the reports I have read, all Kahr does to address this is replace the magazines or followers. Although this might somewhat alleviate the problems, this issue still exists.

This is an excellent firearm in all aspects except this magazine issue. I've spent waay too much time trying to figure out what is going on with this gun, and what I can do to make it reliable. Given what the gun cost, this is something I should not have to do.

Kahr is sending me one replacement follower, and I'll see if it helps. I also have a few ideas that I might tinker with later, but for now, it's going in the safe.

I'll keep you informed if anything new develops.

Many thanks for the replies.

[garyb]

I can see what you are saying about the position of the bullets in the mag. However, I believe the bullets simply go to up to the next position as designed. Mine works just fine. I'm not saying you don't have a problem with your gun, but if all your mags are working the same and all my mags are working the same as your mags....and my PM40 is working and yours is not...(AND you were shooting low, but I am not...)
A+B=C. You've got a gun problem and not a mag problem. JMO.

[jocko]

what gary b says is dead right. Not the mag issue. If ur busint followers on ur kahr 40, then more than likely it is a feed ramp issue. The followers are good followers but no follower is designed to be hammered by a feed ramp. I would also check to make darn sure that no rounds are hitting on the inside of the slide release lever. this will for sure upset th timing of the gun and get feed issues. NO semi that I know of also has an offset feed remp like Kahr does and I believe owns the patent for it also. More than likely their magazines were designed to work with this offset ramp to. I don't know that. I can say I own 3 kahrs and the mags are just fine.

As I have said before, one can do sumpin to a part in a gun that is working fine that will fix anutter part that isnot working fine. We have seen follower mods here that have solved THAT SHOOTERS issue but when tried by anutter shooter, it did not work. Not sure any fix on this forum is ever set in stone, for if every kahr was perfect like mine and many utters, we would not need any fixes or for that matter a warranty..

[muggsy]

I have to agree with Gary. All Kahr magazines position the bullets the same way and most function just fine. I'd like to see some super slow motion videos of a malfunctioning Kahr pistol made with a high speed camera. That could answer a lot of questions.

[garyb]

After a lot of studying, research, and comparison, I have determined that Kahr 40 S&W semi-auto magazines do not operate like every other 40 S&W semi-auto magazine I have looked at. Every 40 S&W semi-auto magazine out there holds all the rounds parallel to each other... except the Kahr. When Kahr mags are loaded full or near full, the rounds underneath the top round are pointed down. This is obvious if you look at the front of the exposed rounds.

Normally, when the slide moves forward, it contacts the upper exposed rear edge of the top round, and pushes forward. As long as the round underneath the top round is parallel with the top round, the top round can smoothly be stripped from the magazine in a normal manner with no excessive friction or catching points. The Kahr magazine is not like this.

On a Kahr 40 magazine, when the slide moves forward, it contacts the upper exposed rear edge of the top round, and pushes forward. Because the underlying round is pointed down, its upper rear edge catches in the extraction groove of the top round. This accounts for the resistance of the slide to move further forward. It also creates a moment, or leverage, on the top round, forcing the front of the round down, and you have the "nose dive."

What is causing this is a loose fit, and excessive flex, of the magazine follower. It cants forward under the higher spring pressure of a loaded magazine, allowing all the rounds except the top round to also cant forward in a nose down position.

To prove this, I temporarily glued a small piece of plastic to the lower rear corner of the magazine follower to improve its fit and resistance to this movement. This greatly reduced the nose down position of the lower rounds, and eliminated the catch in the slide, and the round "nose dive". The flex in the follower still allows some mis-positioning of the lower rounds when the magazine is full, and I suspect that this fix would likely eventually simply cause the follower to break.

BTW, I have confirmed these facts on all three magazines that came with the gun.

Yes, there are many many Kahr pistols out there where this magazine follower flex and fit does not cause problems. In all the reports I have read, all Kahr does to address this is replace the magazines or followers. Although this might somewhat alleviate the problems, this issue still exists.

This is an excellent firearm in all aspects except this magazine issue. I've spent waay too much time trying to figure out what is going on with this gun, and what I can do to make it reliable. Given what the gun cost, this is something I should not have to do.

Kahr is sending me one replacement follower, and I'll see if it helps. I also have a few ideas that I might tinker with later, but for now, it's going in the safe.

I'll keep you informed if anything new develops.

Many thanks for the replies.

I actually looked at this again and much more closely. The top round is nose up AND so are all the rounds beneath the top round. The top round is nose up much more than those beneath it, but none of the rounds is nose down as you describe. You can see this from the front/nose end of the mag, as well as the holes in the side of the mag.
With the slide locked back and the loaded mag in place, the top round sits parallel to very slightly nose up, very slightly...and with the bullet tip almost resting on the feed ramp. Which is why you need to keep it polished.

Additionally, my mag followers are not loose fit and they do not flex. They are so stiff and short, I do not see how this is possible, as you described. Perhaps we have different mags and followers, but this seems unlikely too. When the full mag is inserted in my PM40, the top bullet is pushed down slightly at the nose...like I previously stated to a parallel to very slightly nose up position. I do not see any slop in the follower other than the nose is pushed down slightly when the mag is inserted. Flex? How did you determine / confirm this?

It may be that your gun is doing what you say it is doing, but I have never had a nose dive with my PM40. I do not see any flex in the follower. I do not see any ammo in the mag facing nose down....in my PM. I highly suspect that if the condition you describe exists, your nose dives would be much more consistent, rather than inconsistent. I am not doubting that you see this with your gun, but I suspect the problem is not what you think it is. JMO. Hope this helps you.

[jocko]

never heard of a flexing magazine follower. A newoneonmethatisfor sure

[garyb]

never heard of a flexing magazine follower. A newoneonmethatisfor sure

New to me too. Although I checked mine to see if that was possible. I believe what he meant to say is that when the mag was inserted, the top round's nose pushes down on the mag spring tension at the nose, causing the nose to level out. That is what I see. I don't see any actual follower flex. Can't happen.

[peashooter]

I took the mags all apart and looked at them again. You are correct. The nose dive problem is not caused by a loose or flexing mag follower. Error on my part. My apologies for that.

However, at four hundred round count, the issue still exists where anything above four rounds in the mag creates the first round nose dive. That nose dive is definitely what is causing the slide to occasionally fail to fall forward on its own. And this happens during firing sometimes. It is also likely what is making the gun ammunition sensitive. It barfs badly on Hornady FTX ammo, as described previously.

I have investigated the possibility of a round hitting the slide stop lever. That is definitely not happening.

The feed ramp is polished nicely, so that is not the problem.

I really doubt that Kahr can do much to help, but I guess I'll send it to them and see before I give up.

[jocko]

If u have the extendedmagazine for that kahr, try this. take that extended magazine spring and put itin the flush fit mag and try it and see what goes and what does not.

U can'thurt a thing buy trying this. It will either work right off or it will not.

[CJCM9]

I assume that you have seen this thread.http://www.kahrtalk.com/showthread.php?t=17326

More than the mod to the top of the follower, I like the mod to the legs. "put a 45* on the inside edge both front and back". This allows the spring to slide into the bottom of the follower.

[peashooter]

My search effort did not turn up that thread. I wish it had. That thread precisely describes the issues I am seeing. Thanks for the link! When the replacement follower gets here, I'll have a spare to experiment on. I really like this gun. I want to make it work.


Kahr seriously needs to redesign their mag follower.This is soooo true.

[CJCM9]

The two mods that I did to the follower were:
Sand the two hard edges that could catch on the magazine catch hole
And round out/ramp the bottoms of the legs so the spring can compress into the bottom easier.

Granted, mine is a CM9, but I have only had one FTF and it was not a nose dive.

[garyb]

It appears to me that if the problem can not be sorted out, it might be time to contact Kahr and get the process rolling to get that gun working for you. I feel for you buddy, but you need to go through that pain to get it healed up right, rather than continue to frustrate yourself.

I admit that I have read far too many Kahr follower problems to suit me. But in this case, it might not be a follower problem at all. It might be something else that is not obvious, but correctable by Kahr. You might start to get turned off by the problem you are having and get a sour taste about Kahr guns. Instead, just reach out to them and send the damn thing back to get it running properly....that way you will be a happy Kahr owner. JMO.
Sincerely, I feel your pain and wish Good luck to you.

[peashooter]

I did some basic high-school physics calculations on the angles and forces at work in the Kahr magazine.

The magazine's spring pressure works to press the rounds together into the minimum distance possible. This minimum distance is only achieved when the rounds are all stacked perfectly vertically. The angle of the follower can overcome these forces, but only up to a point.

The ratio of the round's diameter versus its casing length, and the number of rounds stacked, can be used to calculate the limit of angle that can be forced on the stack of rounds.

At the stacking angle of the Kahr 40 S&W magazine, that limit is four rounds. Anything over that number is going to be impossible to force into the angle needed to keep the rounds parallel in the stack.
Other gun makers get around this by either limiting the angle of the stack of rounds, or by allowing additional space for the rear ends of the stacked rounds to move sideways, like S&W does with the Shield, or Glock does with the G36. There is not enough width in a 40 S&W Kahr magazine to allow the needed space to do this.

I have to guess that Kahr considers not having the rounds all parallel to be an acceptable compromise. Given the number of Kahr pistols that function well, it appears that they are right.

I'm also guessing that compromising too much on this angle begins to have an effect on reliability. Maybe eliminating as many variables as possible would reduce this compromise to an acceptable level.

Kahr is sending me a replacement follower, so I decided to experiment with one I already have. The follower does fit loosely, and it does flex some, so I decided to eliminate any compromise there.

I removed the existing polymer lower section of the follower
http://i298.photobucket.com/albums/mm279/phobuc1/DSCN0414.jpg


I fabricated a new lower section out of metal. This fits tighter and has no flex in it.
http://i298.photobucket.com/albums/mm279/phobuc1/DSCN0416.jpg


Here is the new assembled follower
http://i298.photobucket.com/albums/mm279/phobuc1/DSCN0417.jpg


Here is the assembled magazine. Note the modified top of the follower.
http://i298.photobucket.com/albums/mm279/phobuc1/DSCN0418.jpg


Here is the loaded magazine. Almost zero clearance between the fronts of the two top rounds.
http://i298.photobucket.com/albums/mm279/phobuc1/DSCN0419.jpg


And it works! All the "nose dive" issues have disappeared. One hundred rounds and not a single malfunction. Twenty rounds of Hornady FTX, and not a single malfunction.

I would not consider carrying something kluged together like this as a SD weapon. So now, knowing this, I am going to put all the stock parts back in the magazine, send this thing back to Kahr, and see what they say.

[jocko]

just send the email photos, shows what u did,