M&p 9mm to .40

A .40 barrel will probably fit the frame and slide, but the breech face on a 9mm slide is too small for a .40. Not a good idea. Usually it is only reliable to convert a .40 down to 9mm with a conversion barrel, not up. Having said that, I have never done it, so I don't know 100%.
 
A whole .40 top end (plus magazines) would be required. A 9mm barrel will drop into a .40 slide, but a .40 barrel will not fit a 9mm slide.
 
tjhaile said:
A whole .40 top end (plus magazines) would be required. A 9mm barrel will drop into a .40 slide, but a .40 barrel will not fit a 9mm slide.
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I thought I read somewhere that the M&P 9mm and .40 barrels have the same outer dimensions. I have never actually tried, so I don't know for sure.
 
I have an M&P40 and bought a 9mm barrel for it, which works great. My understanding is that the 40 barrel won't fit the 9 slide.
As I recall, my 9mm barrel is thicker than the 40cal barrel. If I get a chance I will measure the OD with my micrometer. If they are the same then I guess the 40 might fit the M&P9 slide.

It would be better if someone with a 40bbl and 9 slide could chime in.
 
themikea said:
I thought I read somewhere that the M&P 9mm and .40 barrels have the same outer dimensions. I have never actually tried, so I don't know for sure.
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The width of the barrel hood on .40 barrels and the corresponding recess in the slide is greater than that of the 9mm. All other dimensions are identical.
 
I do this all the time with my sig p226's 9mm/40sw simply by swaping the slide assembly and locking block, might work for the m&p as well
 
Urbansherpa said:
I have an M&P40 and bought a 9mm barrel for it, which works great. My understanding is that the 40 barrel won't fit the 9 slide.
As I recall, my 9mm barrel is thicker than the 40cal barrel. If I get a chance I will measure the OD with my micrometer. If they are the same then I guess the 40 might fit the M&P9 slide.

It would be better if someone with a 40bbl and 9 slide could chime in.
Click to expand...

You using .40 magazines? I'm curious about how they feed 9mm...
 
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