M&P .45 Mag problem - last cartridge jamming

[Mr. Charles]

Hello, forum.
I have a newer M&P.45 full size that's had about 150-200 rounds through it. It has been cleaned and lightly lubed after each of its first three range trips. It is now consistently misfeeding the last round of each of the two factory mags. After reloading the mag and shuffling the rounds, I have eliminated the cartridge as the problem - the misfed cartridge fires fine when restacked in a different order in the next loaded mag. Problem occurs with a full mag, partially loaded mag and especially with a single cartridge loaded in the mag (making it the last one). It occurs with both of the factory mags provided with the pistol. Mags do not show any visible signs of damage (they are new).
Would this have to do with the pistol having heated up from use? Or just from being newer? Anything I can do to eliminate the problem? Does storing loaded mags (with snap caps) have a negative effect on the springs?
Thanks.

 

[Hamfisted]

Does it do it when you cycle it by hand? Or only when firing the pistol ?


-Mike

 

[RalphMP9FS]

Interesting problem, sounds like the plastic follower in both mags might be out of spec. I would borrow a mag from the range if one is available.

 

[Fastbolt]

What color are the springs? Just curious.

Call S&W and explain the last-round-failure-to-feed concern and ask for replacement mag springs.

If you don't have light blue springs, but an older revision (orange, purple, green, black), you'll also need the revised follower intended to be used with the l/blue springs.

Edited to add that I haven't checked lately, but I wouldn't be surprised if the company's spring vendor has made yet another revision (and changed color yet again).

 

[Mr. Charles]

Springs are light blue. Doesn't jam with snap caps at the kitchen table today. Might be going to the range with wife tonight, so I'll check again when it's heated up a bit. Thanks!

 

[Rastoff]

Would this have to do with the pistol having heated up from use?

It could, but it is unlikely. Try cycling a single live round while at home. I know I don't have to say this, but keep the muzzle pointed in a safe direction.

Or just from being newer?

No, even a new gun shouldn't do this. Right from round one it should work.

Does storing loaded mags (with snap caps) have a negative effect on the springs?

Nope, not at all. The magazines may be left loaded without any negative effect on operation. Snap caps or live rounds makes no difference.

Which mags do you have, 10 or 14 rounds?

 

[dullh]

It is a known fact that some 10rd .45 magazines have been leaving the factory with deformed springs. Take the magazine spring out and look at it...if it looks like Fred Sanfords' hand when he feigns arthritis it is bad and needs to be replaced.

I had two of those deformed magazines. A call to S&W and they sent me two replacements free.

 

[Mr. Charles]

@Rastoff, I have two of the factory 10-round mags.
@dullh, the springs don't look like they're ready to join Elizabeth just yet They are pretty new and have barely been broken in.
Of course, no problem at all at the range the other night. Probably just BECAUSE I posted the problem. Well, all's well that ends well, I guess. Still, it was good to learn about the different colored springs.
Also was helpful to learn that it should be fine to store loaded mags without the springs' rating deteriorating over time.
Thanks for the comments, all.

 

[Groo01]

Groo here
Modern springs are not damaged by being under tension,but
wear out by cycling.
You can keep a spring under tension for tens of years and it will work fine, BUTT if you are one of those that must remove the ammo
every week or so or every time you shoot the gun to "clean and/or lube"
you will find yourself going through springs like a professional shooter.
Like once a year or more.

 

[Mcwsky09]

Have you taken the magazines apart?
Could be the springs are installed backwards.
Can you compare one round loaded next to two rounds loaded to see of the one round sits correctly, high enough, correct angle.
Consistently the last points to the follower and or spring.
Could even be the follower getting hung up on something near the top of its travel.

 

[Sean from Vt]

It has always been my understanding that a failure to feed the last round is a weak or short spring.


Sent from my iPhone using Tapatalk

 

[Louchia]

I agree with Mcwsky09. I would check the followers to see if they have a bur or rough spot that causes them to hang up near the top. Very odd that this happens to both mags. Plastic parts are sometimes the problem. Smoothing off any corners may help or try some kind of lube.

 

[shooter1911]

I had an issue with my 45C in the beginning with the last round of each mag, but it was due to the old bad springs. You have the new blue springs, which is the same spring S&W sent me. The 45C is using the same 10 round springs very successfully.

It sounds like it can only be a few things which would include springs, followers, or magazines. Here's what I would try. Unload your magazines and stand then upright with the base secured on a table top and with a pencil that has an eraser push the follower all the way to the bottom or the magazine. Now very slowly back the pencil out releasing the spring very slow so you can observe if the follower is sticking at any point, especially as you get to the end. If all runs smoothly, I'm at a loss for suggestions.

What ever happens, please let us know.

 

[scooter123]

Feed issues with the very last round in a magazine is typically limited to just a few causes.

One is weak magazine springs or a magazine follower issue. Since this particular magazine design has proven reliable for many years now IMO it's safe to assume the magazine follower isn't a problematic design. I also have a hunch that it's not a weak magazine spring problem because the pistol is just too new but perhaps S&W received some bad springs from their supplier.

The second potential cause is too much extractor tension or a dirty extractor. Use a small brass brush to give the underside of the extractor hook a really good scrubbing at see if that helps. If it does you'll then know it's an area you need to pay attention to cleaning well in the future. Too much extractor tension could be solved with simple use but a much quicker fix would be to return the pistol to the factory to have the extractor "tuned" to provide better feed function.

The third potential area is sharp corners or edges adjacent to the breech face. If you have a sharp corner cutting into your brass as it's fed up under the extractor it can cause feed hangups when the magazine is near empty and the magazine spring tension is reduced. The key to spotting this problem is to save your brass and looking closely for cut or shaved areas on the rim of the cases. You'll also want to look closely at any machining passes that are adjacent to the breech face that present a sharp edge to the case as it slides into position for feeding into the chamber. Fixing this is another warranty issue or something a really skilled Tool and Die Maker can do with a Dremel. Note, using a Dremel to fix a flaw like this will most likely result in the warranty being voided.

 

[Mr. Charles]

Just a quick follow-up. The pistol and both mags have had about 600 rounds through them and the problem continues - intermittently, of course. I just broke down and called S&W. Spoke to Jason at Customer Service who didn't hesitate to say that some of the older mags had that problem. He is sending out to new springs and followers to me. It took longer for my laptop to load the web page than for S&W to help me out. Excellent customer service.

Also confirms many of the comments on this post about older springs and followers. Thanks again, all.

 

[Rastoff]

This just has to be said:

Sorry, couldn't resist.