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Hello everyone, i am new to this but i've been doing some research of my own and calling around to local gunsmiths in my area and so far a few said it was possible to interchange my slide on my m&p 9c to a complete 40c upper slide asm on my 9c frame. From my understanding is that the 9c and 40c frames are identical and will support this conversion. Ive read other threads and seen people say that it is possible and not possible. Im looking for anyone who has done this or has seen / known someone who has done this with no issues. I love my 9c but it would be nice to interchange the slides to shoot 40. s&w. I know you can go from a 40 to 9 with the purchase of a conversion barrel but is it possible to go from a 9 to a 40 with the complete swap of the slide asm? Thank you all for any advice and opinions.
 

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Hello everyone, i am new to this but i've been doing some research of my own and calling around to local gunsmiths in my area and so far a few said it was possible to interchange my slide on my m&p 9c to a complete 40c upper slide asm on my 9c frame. From my understanding is that the 9c and 40c frames are identical and will support this conversion. Ive read other threads and seen people say that it is possible and not possible. Im looking for anyone who has done this or has seen / known someone who has done this with no issues. I love my 9c but it would be nice to interchange the slides to shoot 40. s&w. I know you can go from a 40 to 9 with the purchase of a conversion barrel but is it possible to go from a 9 to a 40 with the complete swap of the slide asm? Thank you all for any advice and opinions.

A quick trip to the gun safe says yes you can swap the 9 and 40 top ends to each others frames, the magazines with fit in either, they appear to function properly. Both of mine a series 1 versions.
 

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As far as I know all you need to do is swap to a .40 cal Barrell and a .40 cal magazine.

Sent from my SM-A515U using Tapatalk

The same quick trip to the gun safe says no this will not work. The 40 case head will not fit in the bolt face of the 9mm slide. So if you want to buy a conversion barrel you need to start with a 40c and get the 9mm conversion barrel.
 

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The same quick trip to the gun safe says no this will not work. The 40 case head will not fit in the bolt face of the 9mm slide. So if you want to buy a conversion barrel you need to start with a 40c and get the 9mm conversion barrel.
Breech face...
 

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A quick trip to the gun safe says yes you can swap the 9 and 40 top ends to each others frames, the magazines with fit in either, they appear to function properly. Both of mine a series 1 versions.
Will 9mm mags function correctly (I don't mean fit in the frame) with a .40 upper?

I ask because the opposite (.40 mags with 9mm conversion barrel) causes issues. Something to do with the feed lips being spaced differently per caliber, is what I was told why many new caused minor problems.

I sold everything .40 related several years ago so I have nothing to try anymore.
 

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Will 9mm mags function correctly (I don't mean fit in the frame) with a .40 upper?

I ask because the opposite (.40 mags with 9mm conversion barrel) causes issues. Something to do with the feed lips being spaced differently per caliber, is what I was told why many new caused minor problems.

I sold everything .40 related several years ago so I have nothing to try anymore.

I put the 40 upper on the 9mm frame, put the 40 mag in, then ran a mag full of dummy rounds through and vice versa. I did not try to use the 40 dummy rounds in the 9mm mag or 9mm dummy rounds in the 40 mags.
 

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Will 9mm mags function correctly (I don't mean fit in the frame) with a .40 upper?

I ask because the opposite (.40 mags with 9mm conversion barrel) causes issues. Something to do with the feed lips being spaced differently per caliber, is what I was told why many new caused minor problems.

I sold everything .40 related several years ago so I have nothing to try anymore.
.40 S&W ammo has a larger diameter case and bullet than a 9mm, so no. .40 S&W ammo won’t fit/feed from a 9mm mag.
 

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It certainly works complete.40 slide on 9mm frame. I’ve been interchanging them for years with different trigger jobs in different frames. You absolutely must use .40 magazines though if you try to run .40 through 9mm frames you’ll ruin the mags.
 

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Hello everyone, i am new to this but i've been doing some research of my own and calling around to local gunsmiths in my area and so far a few said it was possible to interchange my slide on my m&p 9c to a complete 40c upper slide asm on my 9c frame. From my understanding is that the 9c and 40c frames are identical and will support this conversion. Ive read other threads and seen people say that it is possible and not possible. Im looking for anyone who has done this or has seen / known someone who has done this with no issues. I love my 9c but it would be nice to interchange the slides to shoot 40. s&w. I know you can go from a 40 to 9 with the purchase of a conversion barrel but is it possible to go from a 9 to a 40 with the complete swap of the slide asm? Thank you all for any advice and opinions.
I tried it. The barrel extension on the 9 and 40 are different at least on the original versions. the slide and barrel have to match (different widths of the slide extension).
 
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