How does this work?

[Redfish]

I'm a little weak on theory and could use some education. Haven't been to been to shoot the PM 40 yet after it's last "repair". Will soon but have been looking at the thing and trying to envision what's happening when it breaks a mag follower. I've been trying to think it through as happening when the slide goes back into battery after having fired the second to last round and loaded the last one into the chamber. But it just clicked for me that what I did when I got my Lakeline followers was load one round in each mag and shoot it. It marked all 3 followers pretty hard. So this is happening when the slide is moving toward the back? Because the slide comes back farther than the provided clearance before the feed ramp drops and tilts enough to clear the magazine? Assuming that this continues to happen, should I be unloading mid-mag and checking the yet unfired rounds from the chamber for damage as well?
Don

[skiflydive]

Some of the 9mm Kahrs were prone to this a while back It happened to mine. There were several threads about it and the fixes. What I found was the tang (ramp) on the barrel was a little long and the force of the recoil was driving the tang into the front of the follower. It only happens on the last round in the mag because that's the only time the follower is in position to be hit that way. I used an industrial pedestal grinder to pare the tang back about .025". No problems since. It sounds like the same for your gun if it's marking the lakeline followers.

[CJB]

When barrel moves back. Even if a gap, the frame can flex a bit and the barrel hits the follower. Trimming barrel ramp fixes it forever.

[gb6491]

I'm a little weak on theory and could use some education. Haven't been to been to shoot the PM 40 yet after it's last "repair". Will soon but have been looking at the thing and trying to envision what's happening when it breaks a mag follower. I've been trying to think it through as happening when the slide goes back into battery after having fired the second to last round and loaded the last one into the chamber. But it just clicked for me that what I did when I got my Lakeline followers was load one round in each mag and shoot it. It marked all 3 followers pretty hard. So this is happening when the slide is moving toward the back? Because the slide comes back farther than the provided clearance before the feed ramp drops and tilts enough to clear the magazine? Assuming that this continues to happen, should I be unloading mid-mag and checking the yet unfired rounds from the chamber for damage as well?
Don
I concur with what the folks above wrote (especially CJB's point about frame flex).

Some Kel-Tec pistols had a similar issue. Their issue was more centered on damage to rounds in the magazine vice broken followers, but the reason it was happening is the same in both KT & Kahr pistols. This page, http://www.1bad69.com/keltec/smiley.htm (http://www.1bad69.com/keltec/smiley.htm) , does a very good job of illustrating what happens
and what the fix is. FWIW, Avast gives a warning while trying to load the page in Firefox, but not with Opera. That page (and the rest of his stuff) has been around for quite some time and it's an excellent resource.

Based on what I've seen on my CW9, I think there's a remote chance that bullets might take a hit, but possibly with little effect.
My CW9 has not had a follower break (I did break one assembling a magazine), but after installing a Lakeline follower I could see where the feed ramp was hitting the follower:
http://i64.tinypic.com/2uivnsz.jpg
Please note how the hits on the follower are off center; because of this I believe damage to rounds in the magazine was remote in my pistol.

The fix for this was to remove some material from a lower corner of the feed ramp:
http://i68.tinypic.com/20l02dh.jpg
I've not had any further damage to the follower.

Regards,
Greg

[Redfish]

Thanks guys. Tremendous help. Greg, the hits on your follower are in exactly the same place as mine. Will shoot, recheck, and alter as needed. Mine has been ground by both Kahr and me. But neither of us got the spot where your's has some of its sharp edge removed. It's clear from the marks that that's what's hitting. I also notice the grinding under the chamber hood in your photo. Casey at Kahr did same to replacement barrel they put on mine the second to last time it went back to them. He also ground a little of the corner off of it. The gun now throws every casing over my right shoulder without fail. Aside from not hitting me anymore, where to find them is more predictable. Thanks again. I do have a better understanding of how/why this is happening.
Don

[Alfonse]

FWIW, the .40s in particular can have some pretty brutal impact with the follower. I have now seen one where the back leg of the follower was bent. The aluminum can accommodate a certain amount of contact by getting a ding in it, but if it is severe modifications like Greg shows need to be done.

[CJB]

The 40 seems to be the most severe in recoil, and owner of the most problem reports. I think users can agree that the 40 more snappy than the 9 or 45.

Looks like Greg did a real standup job of things. In my way of thinking, do the following:

Use the large size sanding drum for Dremel
Use the coarse sanding material
Hole the Dremel at a right angle "up and down" to the feed ramp to remove the material.... as opposed to at a right angle sideways to the feed ramp. Reason being the follower is curved, and you want to match that curve (with the curved sanding drum) to create the needed clearance. Forget about what it looks like (curved), as the bullet tip gets nowhere near that section of ramp anyway.
Follow up with a Craytex wheel (the rubber wheel with abrasive), then a nice felt wheel with some polishing combound. Don't go nuts with the latter two treatments.

The idea is not so much to "blend" the ramp as to make a distinct clearance in the same. How much clearance? About a quarter's thickness should do.

In all cases, this has fixed the issue permanently.