Chambering the first round, a slingshot modification

[CalBig]

My experience on this issue

So I had/have this issue on my 6-round PM40 mag. 5 rounder works. Also depends on ammo. I think I have slightly more insight in to the pathology of how this is happening. Having the top round in the mag diverge from the rounds below it in the magazine is actually a double whammy for this malfunction. When the noses of the rounds diverge, the end of the brass converges. This causes the rim of the top round to slide in to the extractor groove of the round below it. When the slide comes forward to strip the round, it is stopped at the bottom by the groove, and pushed at the top by the slide. To add insult to injury the nose of the round is unsupported since it's flying in the air. We get the nose dive and the malfunction.

The key is to get the rounds parallel, or as close to parallel as possible, which is what this mod is attempting to do by increasing upward pressure on the nose of the rounds in the magazine. I think the reason we get inconsistent results is that the combination of these two factors can impart and fail to stop a very strong nose-down moment. Until it is possible to get the rounds parallel there will always be a risk of this failure unless your ammo is so pointed (like a typical 9mm FMJ, or Hornaday Critical Defense in any caliber) that the feed ramp is capable pointing the round back up without malfunctioning.

I am going to try to get a better picture of what is actually going on inside the magazine tube when it is full and under spring tension. Is the cheap plastic follower deforming? Are the tails of the rounds coming up in order to allow the noses to go down?

-Adam

[Cornel]

Could someone make this thread "a sticky" one.... iiiiPLEASE!!!!

Cheers!!

OK folks, here's how I did it (it's not a "how to do it", so proceed with caution and at your own risk if decide to attempt something similar)
Note!: While I'm very pleased with the results of these mods, some folks have tried modifying the follower (though not exactly as I did) and not had the same results (to varying degrees). It could be that I just encountered a "perfect storm" with this mod and my particular gun. If you attempt something similar please keep this in mind and be sure to read their posts.

First off I want to give some credit where it is due. I’m sure many here have seen this video: http://www.youtube.com/watch?v=LPa3MtWkias
Basically, the maker of it suggests the use of a ProMag magazine to facilitate loading the first round from a magazine.

I finally acquired a ProMag (thanks Jim) for a little hands on research. ProMag has something of a less than stellar reputation on the internet. I’m not going to try and change that because, after seeing this magazine, I believe it’s warranted. I do need to mention that this magazine was used, so read the following with that in mind. My ProMag is a ten round magazine; I found the spring is totally inadequate for that configuration. To compound this, the follower is rough and oversize. The magazine would only feed two rounds before a nose dive stoppage on the third round. However, it did feed the first round easily; now is that because of the loose spring tension (my Kahr will usually feed without issue from a downloaded magazine) or something else. After a little comparison, I decided to eliminate the magazine tube from the equation and opted to try the ProMag follower in a Kahr magazine. My first thought here was use the Kahr spring, but it will not work with the follower unless the follower is modified to accept it. Speaking of modifications, the follower needs to sanded on it sides and rear to function without binding in the Kahr tube. I tried installing the follower with the ProMag spring and was able to fit it all in the Kahr magazine tube. This combination allowed for a capacity of 7 rounds (just like a complete Kahr unit). It also put the rounds under much more spring tension. Bench testing confirmed that the top round still fed easily and that the follower would lock the slide back. Testing in the field, the magazine functioned without issue. If the ProMag spring will hold up, I believe this is a viable modification as is.

Here's the ProMag follower/spring in a Kahr tube at work: http://www.youtube.com/watch?v=CYYZrSqGTdk

I’m not inclined to trust that spring; beside that, I’m not sure where to find a replacement if need should arise.
As it did put comparable (to an OEM magazine) pressure on the top round, I decided that the follower is the reason this all works. Now, I probably could modify the follower to work with the Kahr spring and be done with it, but after some study thought I could modify the Kahr follower to work and eliminate the need to buy extra parts.

What I did to the Kahr follower requires a pencil and some sand paper.
There is a transition point on the Kahr follower where the front portion of the feed surface slopes downward from the rear section. I decided this needs to be reduced and moved forward. I did this by wrapping the pencil in sandpaper and sanding along the rear plane of the follower maintaining it original angle. This did not totally solve the feeding issue, but perhaps it might if you took it further than I did. Then again, you risk sanding through the top of the follower. Next, I sanded the top of the follower, reducing the two ridges there. I did this by laying the sandpaper on a flat surface and sanding the top by moving the follower (again maintaining the existing angle). Now we’re cooking! Bench testing results were great as the top round feeds much easier than the stock configuration and there is no change to how the slide locks back. My previous video shows how it works, but here's another where I somewhat ride the slide home:
http://www.youtube.com/watch?v=ogM036r016M

How to sand:

How much to sand with the pencil backed sandpaper:

How much to sand using a flat surface (just under .06" on the calipers. I suggest repeated testing as material is removed to preclude manufacturing tolerances causing any issues) :

Finished:

For comparison:


Update - I had an interesting development:
"... I had both mags apart yesterday and upon reassembly, both required brisk manipulation to feed hollow point (no more riding the slide). I was dumbfounded by this development, but figured it had to be something I had done. A quick checked showed that everything looked good (parts were clean and installed correctly with the springs properly orientated). I decided to flip ends of the springs and was back in business after doing this. While this worked, I've no clue why other than there is the slightest difference between ends of the springs (and on both springs). The end that seems to have a less steep angle on the last coil needed to be at the follower. I'm going to follow this up when the new springs arrive."

So for now, I'm pleased with my modified mags, but want to do more testing. (as of 5-27, make that "very pleased" )
Regards,
Greg

[kpm9]

Just wondering if there is any interest in a modification to the Kahr 9mm follower that makes chambering a round via the "slingshot method" much easier and consistent

A solution in search of a problem?
Never been an issue for me. All my Kahr's slingshot fine.

[gb6491]

A solution in search of a problem?
Never been an issue for me. All my Kahr's slingshot fine.

Good for you and thanks for sharing your thoughts. As I stated earlier in the thread, I could/can "slingshot" my Kahr pistols as well. However, my CW9 was very technique sensitive (requiring a very brisk overhand manipulation of the slide). This mod simply makes manually chambering a round in it much less technique dependent. To my mind, having a larger window for success is a good thing in a defensive pistol. As always, YMMV (I guess that applies to opinions too).
GB

[Bawanna]

I think it falls into the making a good thing even better category too.

I can also slingshot and could out of the box but if something like this improves my chance of success as you say, that's just gotta be a good thing.

[yu2010]

Hi, GB6491:

I have a PM40. Will your mag mod work for PM40?

I would like to learn how you did it to your PM9.

Thanks.

Yu2010

[Craig_PHX]

What if you just put some J-B Weld on the top of the follower to get rid of the transition all together? Then you would not have to dink with anything except the front portion of the follower.

[mightymouse]

My experience with JB weld, is that with some poly plastics, 6/6 nylon it doesn't adhere well. I don't know what the follower is composed of but I can imagine a chunk of epoxy floating around at a crucial moment.

[garyb]

I'm always willing to learn something new especially if it is an improvement, so please share your details. I have not had a problem with my PM40 either way (Kahr's way or slingshot method). I wonder if your mod is something worth applying to the PM40 as well as the 9???? Anxious to see what you've done. Thanks in advance for sharing what works for you. Well done.

[jocko]

I guess I will go with the IF IT AIN'T BROKE, DON'T FIX IT. theory.

[JFootin]

Petition

I think we ought to start a thread called: "Petition For Design Improvement For Kahr Magazines." Make it a sticky on the Magazines page. Start out with a statement that we don't buy Kahr's statements about perfect functionality and no need for changes. Point out how they have had to address the weaknesses in the design by putting instructions in the manual about using the slide stop to feed the first round. Put a long list of links to threads discussing magazine problems and, of course, highlight this thread as having some valid ideas for design changes. Encourage every member to sign the petition, and give a link to the thread to anyone reporting magazine problems. Then, get JohnH to present it to company management. Just saying.....

[Denny M]

+1 with JFootin!!

[Bawanna]

I think we ought to start a thread called: "Petition For Design Improvement For Kahr Magazines." Make it a sticky on the Magazines page. Start out with a statement that we don't buy Kahr's statements about perfect functionality and no need for changes. Point out how they have had to address the weaknesses in the design by putting instructions in the manual about using the slide stop to feed the first round. Put a long list of links to threads discussing magazine problems and, of course, highlight this thread as having some valid ideas for design changes. Encourage every member to sign the petition, and give a link to the thread to anyone reporting magazine problems. Then, get JohnH to present it to company management. Just saying.....

You sound like a gosh darn rabble rouser to me!




I always told yer momma you was gonna be a good boy and do something good someday. Maybe this is it?

[JFootin]

You sound like a gosh darn rabble rouser to me!

I always told yer momma you was gonna be a good boy and do something good someday. Maybe this is it?

Well, they used to call me Wild Dog in high school. But I just don't think it is right when customers are having to re-engineer their magazines to make them work right! :31:

And it is obvious from this thread that just a little creative thinking is all that is needed to solve this ongoing problem! If someone—anyone—at Kahr would just listen!

Maybe they are afraid of litigation if they ever admit there is something wrong with the magazines. But, gun makers fix and improve gun designs all the time, so why not fix this? Is there any one thing that you can think of that would make a greater improvement in the entire line than this? I don't think so!

[O'Dell]

funny, Ihave no issues with the kahr magazines in racdking a live round into the gun in my K9 or PJM9 or P380. Kahrs magazines are waht they are by design, not by accident. I credit thatto the offset feed ramp allowing a lower bore axis and there fore a more pleasant gun to shoot than most.. It's only a drwaback if you allow it to be that.

I agree - I've never had a problem racking the slide to chamber the first round either, although I know Kahr doesn't recommend it.