Does it matter which way it goes in the mid/fs?

I think I've got the M&P bug bad. I want to get another, especially since everything is 15% off at the store I purchased my 45c from.

I'm interested in a mid/fs for home/range. I'd use it as my trigger/targeting instead of burning thru .45 at $.40-$.50/bullet!

And maybe I'm answering my own question, but I'd prefer the .40 as the personal protection caliber. So, does it matter which way the conversion goes? Because if not, I would probably start w/the 9 & buy the barrel/mags later.

I think . . .

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Gen1 4513TSW
M&P 45c

Ain't gonna work.

9mm and .40S&W require different slides, magazines, and barrels as the cartridge cases are different diameters.

.357SIG (merely a fast 9mm) is a necked down .40S&W case so this cartridge just takes a barrel change to shoot from a .40S&W pistol.

-- Chuck

Buy the 40 1st, Storm Lake makes the 9 barrel. It's awsome, I bought the combo for my FS. I just put a 40c on layaway and plan to do the same. All you will need is a barrel and a magazine. Everything else stays the same. The way I understand it is you can can go from the 40 to the 9 but not the 9 to the 40..

Happy New Year

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Jack C

KKM makes the 40 to 9 conversion also.
M&P 40S&W and 357sig Full 9mm Conversion Drop-In :: S&W M&P Full :: S&W M&P :: KKM Precision :: Reliable and Accurate Custom Pistol Barrel Manufacturer

Even if you could go the other way I wouldn't recommend it. You would want your defensive caliber to be the most reliable.

You do have to go 40-9 if you do. The 40 breechface is slightly larger and the slide is slightly heavier, they both use the same recoil spring. You might have trouble cycling light 9mm loads and may need a lighter recoil spring for consistant ejection.

I bought the 40...then a 357 sig barrel, now I have a 9mm barrel and and new mag. 3 guns in one its awsome. I used storm lake barrels. You can get different lengths, ported and I think threaded are your options. As stated above you can't go from 9-40 as the breach face is larger on the 40...you can go 40-9 as long as extractor grabs brass good....no problems here.

Question --Storm Lakes said it takes 6-8 weeks for a 9 mm BBl to be made for an M&P 40 c-- is this new or was it always this long to get one --also what magazine do you use a S&W or is there another aftermarket just as well suited??

Thanks for the help

I bought a factory 9mm barrel and mags, and tried it in my M&P 40. I did a measurement comparison and then a range test. I posted this on AR15.com-

9mm M&P barrel in a .40 S&W-a photo comparison-UPDATE IN OP-Range test - Page 1 - AR15.COM

Was this test based on a standard M&P 40 as opposed M&P Pro 40. Could the same been done with a M&P Pro 40 using a 9 mm barrel for a M&P Pro 9 and 9mm magazine?

It would probably work for the Pro Series as well. If someone has a Pro 40 and can take some measurements, I have a Pro 9 that I can measure.