Will the M&P 40/357sig magz run the 9mm rounds?

[JoeyEcko]

I have an M&P 40 FS and ha it have run 100% shoots great way better than me but sense the .40 rounds are about 85% more expensive than the 9MM over here in P.R. I anm looking to get the 9MM barrel from Smith&Wesson so I could save a good few $ or even better get more ammo to shoot with at the range. Sense ive read that some people use the .40 magz to shoot in the 9mm barrel I just wanted to know what problems could i hve using those magz or if I should get the 9mm magz with the barrel?.

 

[RH45]

I never tried it with M&P mags, but, with MOST of my Glock mags, I could run 9mm, in the ,40 mags.
You'll find out right away if you can load the mags, and the rounds stay in the mag.

 

[1sailor]

I was able to do it at first with very few problems (last round usually wouldn't feed though). But as the magazines got more and more broken in the 9mm rounds started fitting more and more loosley. I finally broke down and bought a couple of 9mm mags.

 

[JoeyEcko]

Good to know thanks for the imput

 

[1sailor]

Just as a followup. Since buying the two 9mm mags I have put over 5000 rounds of 9mm downrange. In all those rounds I do not recall ever having one single failure of any kind. These really are great pistols.

 

[Capt Crunch]

Before I got my 9mm barrel (this is for my 40c BTW) I tried cycling 9mm through it by racking the slide and it seemed to work just fine. Oddly enough however, once I got the 9mm barrel it jams up after the first one or two racks of the slide using my .40 mag. I'm going to go ahead and buy a 9mm mag and test it out as soon as funds allow but I'm not expecting any issues after that.

 

[Number1gun]

Try changing to 9mm mag folower. That should help..of course having dedicated mags in each caliber makes more sense.

 

[Capt Crunch]

Try changing to 9mm mag folower. That should help..of course having dedicated mags in each caliber makes more sense.

Yeah, just seems rather silly to go through changing the follower, I'd rather just get a new mag

 

[Mr.40]

For $20 you can get factory mags from botach tactical and not worry about reliability. That's what I did, works great!

 

[Houdini1953]

In my opinion it is a good option for shooting at the range but unreliable if used in self defense then it becomes your own opinion after some real world experience trying it out and that would be a scientific approach but with the results from others perhaps you might take some advise instead of costly experimentation and just buy a 9mm magazine or two and save your self the reinvention of the wheel!