A few weeks ago I started having feeding issues big time.
I've got about 12K through one of my M&Ps and this was unusual, so started doing some more detailed investigation.

I took all my mags apart and found 3 followers that were cracked, broken or missing pieces.   They were all the first earlier generation mags.  I have had no problems with the newest style followers.
Below are some pics that may help you in determining which generation you have and what to look for.  

Front view.  Older on the left, newer on the right.  
There is a distinct difference and you can see how much more robust the new one is.
There is a very clear molding line on the old ones.  1 was cracked all the way across and bent up under.  1 was just starting to crack along that same line, and the other was missing a piece.
The new ones also have the caliber stamped on top.


Rear view.  The new ones have much more material.


Side view.  You can see how much more steep the angle is on the old follower, which I'm sure contributed to the weakening of that molding seam.


Piece missing.  Here you can really see the molding seam, which is not present on the new style.



Check those mags and hope this helps.

Thanks for posting that; I'm fairly certain that have the 1st gen followers in all my M&P mags, but nowhere near the round count that you have through yours. I'll make sure to check them out, though.

Where did you get the new ones? SW? free?

Speedshooters specialties

Those pictures are of 2nd and 3rd generation 9mm followers. First generation was black.
There are three generations of 40cal followers also.
All 45 cal followers I've seen have been the same.

Posted updated accordingly.
Thanks for keeping me straight

I've had 4 mags fail on me.  2 at about 2k, 2 replacements at about 1500 later.  I think all were early generation.


ETA:  All were early Gen .40 followers.  Just received 2 new replacements, and both have the early generation followers

Hmmm, can't see the pics any longer.  Did they get moved?

My last trip to the range I had a few first round only feed problems with my M&P40.  Was shooting PMC FMJ .40 and the flat face of the bullet was actually getting caught on the end of the feed ramp.  The copper jacket is obviously soft enough so as to leave a bite mark from the feed ramp.  My solution as the time was to remediate:  safely lock the slide to the rear, eject the mag, reseat and rotate the round to move the bite mark out of the way, re-insert mag, release the slide to chamber the round.

It eventually worked, but one or two rounds ended up having multiple bite marks.  This happened probably 4 times in a 100 round range session.

Again, first round only.  Next time to the range, I'll just load 14 rounds and see if I get the same result.  I have had this happen on my personal defense ammo, but haven't shot nearly as much of that, and never after the first round (which could eliminate the concern, since I carry one in the pipe).

Um, pic links are broken. Worthless thread to be tacked if the pics are gone.

I can still see the pics. I need to update 3 of my mags to the new follower

And another 400 rnds and it's failing again. Guess I need to order new followers myself this time since smith can't do it right.

Thanks for the posting.  All of mine are the older style followers.  As soon as I hear back from the supplier mentioned I am going to order all new followers.

Thanks for posting. My M&P 9 FS is a late 2010 model and I just checked and it came with new followers as well did the mags I bought recently.

Thanks for sharing the knowledge!

I figured this out yesterday.

On my bad mag, the distance between the nose of the first round and the front edge of the mag housing is slightly shorter than the good mag.  I'm able to consistently replicate the issue on the bad mag now.

Call S&W's customer service number and they will ship you the new ones for free, no questions asked other than how many do you need. They really are a first class manufacturer.

Do the black gen 1 followers have the same failure problems?

I have two first generation M&P9 mags with black followers that I got with the pistol when I bought it new in 2006.   I've used them a lot.   I also have another first generation mag and follower that I bought later.  No problems with them so far.  The first gen springs were weaker than those in the newest generation mags even when the older gen mags were brand new.  Short answer is no, not in my experience.


TS

It seems like the plastic S&W uses for followers, and has used for some time isn't holding up too well. I have a 4506 and a 5906 now, and have had a 4006, and bought a bunch of used mags for them and many of them needed the followers replaced. Some were broken, some looked like they were just falling apart due to (Guessing here) solvent eating up the plastic. The 4506 mags were the worst, all but one of the followers in the two mags that came with it and the three I bought on gunbroker were bad, easily seen when I took them apart to clean/inspect them. At least one "leg" on each was broken, with the loose piece laying in the bottom of the mag, or it was still barely attached. The 4006 had just one bad one in four used mags, the one I got with the gun. I went online and ordered replacements and had no issues, the 5906 shot fine with the bad followers.

A friend of mine liked my 5906 so much, he went on the auction sites and found a great looking one, in the box, with 7 mags. All but one had bad followers that looked like the one in the pics. The "legs" were cracked or broken off. Just like with my gun, it didn't bother his gun much and only one mag was "bad". He bought a bunch of followers and they were the stronger, "no leg" design.

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E mailed S&W told them I would like some of the new style magazine followers.



UPDATE

I sent my firearm in for repair a couple weeks ago and got these..

M&P 40c magazines.

.

Smith and Wesson changed the 9mm magazine followers again

The pad for the last shot hold open has been inlarged and it has a more pointed top to it.

New one on the right received 5-1-16

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right  one was installed on two years ago

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gotta love s&w's commitment to perpetual innovation and improvement. although you got to hand it do them, usually it only takes a version 2.0 for them to get it right

come to think of it, time for a boydguard 2.0 plus with metal insert chassis, a 1911 thumb safety style, and big boy grips?