9mm 17 Round Mag Jams - MP-Pistol Forum

9mm 17 Round Mag Jams

This is a discussion on 9mm 17 Round Mag Jams within the MP Pistol Tech Help forums, part of the Smith & Wesson MP Forum category; I encountered a problem where two of my 6 mags were jamming ammo after about the 9th\10th cartridge was put in. It appears as if ...


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Old February 18th, 2015, 07:29 AM   #1
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9mm 17 Round Mag Jams

I encountered a problem where two of my 6 mags were jamming ammo after about the 9th\10th cartridge was put in. It appears as if two cartridges jammed by one of them rotating down and wedging itself in between the mag wall and the cartridge below it. I was using Federal 9mm 115 grn RN from those 100 round "Value Size" boxes.

The mags were recently cleaned and only had about 50 - 60 rounds (10 at a time) through them since the cleaning. The follower appeared to be fairly clean. A lot cleaner then my other mags that I was shooting my reloads through. So I don't think this could have been a dirty mag issue.

When the jam occurred I disassembled the mags, fixed the problem and went on my way. But after I reassembled them, it dawned on me that my followers could have been put on backwards. But I didn't notice that when I took them apart. And I didn't look for that problem either while disassembling them. I'm not even sure if it's possible to put the follower back in backwards, but I can't imagine that I would have not noticed doing so after cleaning the mags. And if so, how come the mag worked just fine for the first 50 rounds before it jamming on the next 10.

I'm going to clean them again tonight after work and make sure that the followers are properly installed (and check to see if they can actually be installed backwards). But I'm wondering what are the common causes of mag jams and what I can do to prevent them in the future. Also, what is the service life of a genuine S&W 17 round 9mm M&P mag? It's only ever seen range bench time. No dropping to the ground or abusive use. They probably have less then 300 rounds through them each.

Any advice would be appreciated. Thanks.
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Old February 18th, 2015, 09:00 AM   #2
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Those mags are good for 20-30 years easily. In rough competition use where they are regularly ejected to the ground and in the dirt, it would be quite a bit shorter.

I'm still using S&W mags that are over 40 years old, still have their original springs and are stored loaded, they are still fine. Those only get light use, but are left loaded 24/7 and 365 days a year.
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Old February 18th, 2015, 10:43 AM   #3
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Thanks for the reply. I'm glad to hear that the mags should last a long time.

Are mags covered under any S&W lifetime warranty like firearms?

Are "bad" mags a common enough occurrence that it's possible I just got too bad ones that are now acting up?
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Old February 18th, 2015, 10:55 AM   #4
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I've never had a bad M&P mag.

My original four from '07 are all working just as well as the other six I have that are only a year or two old.

Also, none have ever been taken apart for cleaning, but then I don't drop them on the ground.
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Old February 18th, 2015, 03:05 PM   #5
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You might want to check the OAL of your ammo before blaming the magazines. Bad M&P magazines are uncommon, 2 bad ones in the same kit is almost impossible.
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Old February 20th, 2015, 11:16 AM   #6
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So I checked my mags and there is no way to put the follower in backwards, like I assumed.

I checked the COL of the ammo I was shooting and got measurements in the 1.141" - 1.15" range. According to my Hornady load book, 1.165" is the maximum COL. But I'm use to loading my reloads to 1.1" I'm not sure if those values are too high for the M&P. Or possibly the package had a few cartridges that were over the 1.165" limit and those were the ones that stuck.

Either way, I still don't have an answer to this. So I'll just keep an eye out for other occurrences and see if I can save the ammo that got stuck and measure it when I get home.

Thanks to everybody who gave advice and knowledge on this.
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Old February 20th, 2015, 12:55 PM   #7
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Are they still doing it after you disassemble, cleaned and reassembled?
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Old February 20th, 2015, 01:37 PM   #8
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Quote:
Originally Posted by KRWeiss View Post
You might want to check the OAL of your ammo before blaming the magazines. Bad M&P magazines are uncommon, 2 bad ones in the same kit is almost impossible.
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Old February 20th, 2015, 03:06 PM   #9
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I've got a couple from the early 70s I think. You may have the springs in backward. That's possible and I've seen it cause all sorts of goofy problems (never in my own, of course, I'm way too smart to ever do anything like that. And I believe terrorists just need jobs, too)

When the spring is in correctly, the last slanted portion of the spring goes to the back of the mag and the two longest "legs" on the follower go to the rear also. The "hump" on the top of the follower goes to the left side as you are looking to the front of the mag. Be sure to wipe the spring, the inside of the mag, and the sides of the follower with some light oil or some other lubricant.
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Old February 20th, 2015, 05:24 PM   #10
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Quote:
Originally Posted by jwh321 View Post
I've got a couple from the early 70s I think. You may have the springs in backward. That's possible and I've seen it cause all sorts of goofy problems (never in my own, of course, I'm way too smart to ever do anything like that. And I believe terrorists just need jobs, too)

When the spring is in correctly, the last slanted portion of the spring goes to the back of the mag and the two longest "legs" on the follower go to the rear also. The "hump" on the top of the follower goes to the left side as you are looking to the front of the mag. Be sure to wipe the spring, the inside of the mag, and the sides of the follower with some light oil or some other lubricant.
The polymer framed M&P pistol and accompanying mags that the OP is concerned with weren't made in the '70's.

I believe that my first M&P9, bought in 2007, is one of the earlier ones.

"Lubing" a mag is unnecessary, and can cause powder fouling and other contaminants to accumulate in the mag.

None of my 10 M&P mags have ever been dissembled for cleaning, much less "lubed."

I don't even lube my 1911 mags, which certainly aren't a high tech, or new, design.

Last edited by Rick M; February 20th, 2015 at 05:30 PM.
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Old April 10th, 2015, 11:47 PM   #11
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I agree with jwh321. Check proper assembly of your mags.
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