9mm mags for MP40

luckey

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Just pulled trigger on a storm lake conversion barrel for my MP40. Any suggestions on the 9mm mag that is cheap and reliable. Thanks!
 
From everything I have read to date, you need to use the 9mm mag and the factory one seems to work the best. When using the 40 mag, it has feeding issues, so best have as little issues as possible and use the right mag. Let us know how you make out !
 
No. this won't work for MP40 and G22. It has to be the MP9 and G17 mags. i just want to see if there are something cheaper with the same reliability out there. after all, the reason I bought the conversion barrel was to save a few bucks.

I think you are thinking about CZ(can't remember exactly). I don't have personal experience with it, but read somewhere that for CZ, some people claimed they can use Jericho .40 mag to hold 13 or 14 rounds 9mm and work just fine.

I'm pretty sure you can just keep using the .40 cal mags.
 
13 allegedly.

Anyone tried to run .40 M&P mags in an m&p9? I'm tempted to pick one up and see if they feed well or not, I'm going to have to do a little internerd searching now.

Hmm mixed reviews, seems the feed lips are a kunt hair wider on the .40 mags than the 9mm mags. Otherwise the .40's fit fine in the m&p9. One guy annealed bent and re hardened his which then fed without issue. Reliable always has a bunch of .40 mags on the shelf for 45$, might have to grab one and test it for curiosity sake.
 
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Anyone tried to run .40 M&P mags in an m&p9? I'm tempted to pick one up and see if they feed well or not, I'm going to have to do a little internerd searching now.

Hmm mixed reviews, seems the feed lips are a kunt hair wider on the .40 mags than the 9mm mags. Otherwise the .40's fit fine in the m&p9. One guy annealed bent and re hardened his which then fed without issue. Reliable always has a bunch of .40 mags on the shelf for 45$, might have to grab one and test it for curiosity sake.

latest addition to the RCMP watch list.
let us know if your transfers start taking a little longer.
 
latest addition to the RCMP watch list.
let us know if your transfers start taking a little longer.

Haha, put your tinfoil hat away. I meant try to use a stock .40 M&P mag in my 9mm, not modify a .40 mag.

If you want to look at it that way, bending a feed lip is not really modifying a .40 mag to fit in. 9mm. It already does that on its own from the factory, nor does it affect the legal limit it can hold of its designed for caliber.

Oh... wait I hear the black helicopters already.

Man, paranoia runs rampant around here sometimes...
 
So for the sake of curiosity I bought a m&p .40 mag to test in my m&p 9mm, now let me clarify from the get go that I have not modified nor do I have any intention of modifying the .40s&w mag in any way.

That being said here's what I found:

-.40 s&w m&p mags will hold 12rnds of 9mm and fit in a m&p9, basic dimensions are near identical.
-The fees lips of the .40 mag are a kunt hair wider than the 9mm mag lips. This makes the angle the 9mm round sits at steeper.
-9mm out of the .40 mag will manually cycle, it loads and extracts manually until you get to the 12th cartridge.
-The notch on the front of the follower ramp that engages the slide lock and sits higher on the .40 mag, when the 12th round is ready to load the slide is locked open.

So, without modifying the notch to sit lower. You will have to release the slide lock manually in order to load the last round if shooting 9mm out of a .40 s&w mag. I will test it next time I go shooting and will report back with how it loads and functions while actually shooting and not just cycling manually. It's a shame the slide lock engages in the last round, if it fed the last round it would be worth picking up a few more to squeeze a few more 9mm rounds into the equation legally. Will be interesting to see if it feeds reliably with the wider feed lips, worst case scenario I'll either sell the .40 s&w mag or buy a m&p.40 to go with the mag lol.

Here are some pics, so you can see the angle differences etc.



 
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So out of 60 rounds I ran in the .40 s&w m&p mag I had one jam which when I pulled the slide back a touch then chambered like normal. I had to release the slide to chamber the 12th and last round which I already knew would be the case, I actually didn't find it a pain. My right support hand easily trips the ambidextrous release on the right side of the M&P9, I don't need to change the grip of my dominant left hand at all while releasing and firing the last round.

So in my M&P 9 it seems to work well enough, it jammed around round 6 of 12 when I was doing a quick mag dump. When shooting at a steady pace or even shooting double taps it ran great, might just have to grab another. I have to say shooting more than 10 rounds was nice for a change.
 
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