What causes the cracks in the mags?

[Orphanedcowboy]

I have had 2 6rd "K420" mags crack at the rear upper portion. It doesn't seem to be an overwhelming problem from looking at the various forums.

On a side note, I called Kahr and they are sending replacements asap so that makes me happy.

[JFootin]

My opinion, and probably not worth 2 cents, is that the mag is riding a few mm too high and getting slammed by the bullet stripper on the bottom of the slide. That seems to me to be the only thing that could put that much of a hit on the mag. Maybe this is caused by an out of spec mag catch window on the mag. I think this could be eliminated if Kahr would redesign their mags to flush fit into shaped recesses on the bottom of the grip frame like Glocks and many other guns. The way they are now with the gap at the bottom, it is all up to the mag catch to determine the position of the mag in the gun. And the gap allows for the possibility of a mag being pushed up too far where damage can happen. JMHO. YMMV.

[Thunder71]

Squeezing them in a vice.

[OldLincoln]

Metal cracks because it is flexing. If the new mags also crack I would ask Kahr about the poly frame. Or as Thunder said.... if you do squeeze them, do it in the middle not close to the edges.

[jocko]

I go withg JFopotin analysis. alot have broken in less than one magazine load, not 9ndicative of weak steel. I don't buy the squeezing thing either as most all have broken without anything ever being done to them. I think tha tis also why kahr sometimes wants the entire gun back. It seems more prominent in the 45's for some reason. It takes alot of violent force to crack some of the magazines the way we hav eseen them. We will never know, for I don't see kahr saying aything about what is going on other than they will fix the issues..

[Tilos]

The mags become "work hardened" from the bending/forming process and crack in the corner, where the metal is stretched/coined the most.
They could be annealed and re-hardened for uniformity but this would add cost to the process.

I've never seen a cracked mag but ask those who have, was there any score marks on the inside of the corners that cracked.

Any tool marks inside could create a stress point for a crack to start.
I can tell from the finish that the mags are tumbled/shot peened on the outside to smooth the surface but have not looked inside of one too closely.

just guessin'
Tilos

[jocko]

imo IT IS NOT A MAG ISSUE. U sure don;t read about this mag thing in other gun makes, and certainly if it happens is is so so rare for other gun makers that it isn't even discussed as an issue. companies that make magazines for a living certanly know how to make magazines, so I aint buyin the mag thing.. Just sayin

[Orphanedcowboy]

I looked at the mags, and none, including the cracked ones are showing any evidence of the slide catching the mag. I looked at the 3 7 rdrs I just sold and the 4 6 rdrs I have. The ones that are cracked are packed up and on their way to Kahr now. I wished I would have broke them down and had a good close look at them. I did take a quick look at the interior prior to shipping and they looked to be finished just as well as the others.

[CJB]

Gonna mildly disagree with Jocko... its been a problem in the past for Colt, Randall, Metalform, IMI (Israel), Browning, MecGar, probably others. I've got Colt and Randall magazines with cracks that I still use for range use... since they still work "ok".

Just my 2 cents - magazine steel is fairly brittle stuff, and they've put some nasty folds in it. That being given... now consider forming dies and the metal itself. Its always a juggle fest when dealing with manufacturing an item where the incoming raw material (the steel) may not be exactly the same from run to run. Then you got slightly dissimilar steels and the heat treatment (and or pre-stress or post-stress relief).

Remember the OLD Colt magazines where only the tops were heat treated? You could see the flame treatment they got... maybe they had something there.

Bottom line - occasionally, all variables in mags, and pistols alike, you get a mag that cracks, maybe a whole run of 'em that is prone to cracking. Wish it wasn't so, but its not totally new territory to cover as far as problems go.

[jocko]

I did not know that, one seems to not read about those issues nearly like kahr has with them. I still feel it is a gun related thing more than the magazine, but I can't prove otherwise. We tend to look at the end result of an issue, (like cracked magazines) and always blame the magazines. Lately kahr has ask for some of the guns to be returned with the split magazines. That to me was some sore of indicator that it could be gun related. I think it was wyn who had alot of split magazines and correct me if I am wrong but I think it took an entire new gun to get him right.

We have seen some magazines split in the first usage. I can say that my new P380 when I bought it, the one magazine split in the first half dozen loads. It has never given an issue since with the magazines...

[Tilos]

CJB:
To your point and as I mentioned before, a minor scratch on the tooling that's used to bend/form the shape could transfer to many, many mags in a high speed manufacturing process.

Once a large amount of mags are accepted from a vendor, and later found to have some defects in use, the only choice would be to have a recall or deal with it on an individual bases by replacement.

It seems Kahr has decided to replace any that prove defective in use.

I'll ask anyone who have delt with this issue, has Kahr asked for the GUN to be returned or just the mag??

Again, a stress point could be so small as being undetected with the naked eye.

Orphanedcowboy: Thanks for posting.

Tilos

[muggsy]

The mags become "work hardened" from the bending/forming process and crack in the corner, where the metal is stretched/coined the most.
They could be annealed and re-hardened for uniformity but this would add cost to the process.

I've never seen a cracked mag but ask those who have, was there any score marks on the inside of the corners that cracked.

Any tool marks inside could create a stress point for a crack to start.
I can tell from the finish that the mags are tumbled/shot peened on the outside to smooth the surface but have not looked inside of one too closely.

just guessin'
Tilos

Tilos, as a machinist I agree with your analysis completely.

[michpatriot]

pics

We really need pics.

[Orphanedcowboy]

It seems Kahr has decided to replace any that prove defective in use.

I'll ask anyone who have dealt with this issue, has Kahr asked for the GUN to be returned or just the mag??

Tilos

They only asked for the magazines back, even shipped two prior to receiving them as well.

We really need pics.

That was an afterthought once they were already in the mail, sorry.

[CJB]

I did not know that......
..... kahr has ask for some of the guns to be returned with the split magazines. That to me was some sore of indicator that it could be gun related. I think it was wyn who had alot of split magazines and correct me if I am wrong but I think it took an entire new gun to get him right.

I'm not sayin' that it can't be the gun, I'm just sayin' that cracked magazines are nothing new under the sun. Could also be that Kahr wanted to rule out the gun, or... they knew something they're not saying, or both.

Its ok Jocko... I think we're really on the same page... I'm just giving some horizontal leeway to the whole discussion