...buy an M&P in .40 cal and replace the barrel with one for 10mm?

Would the magwell have room?

There was some who investigate that conversion, the mag well and magazines were too short to accommodate the longer 10mm.  However the 45 M&P could work if someone made barrels chambered for 10mm with the outsides keeping the same as 45 profile.  It would be simpler if S&W would just make the M&P in 10mm.

Thanks for all the feedback.

I know that making custom barrels for rifles is not unheard of.  Do people do the same for pistols?

They do, but it is not in the same ballpark as far as cheapness.

I have come so close to buying a M&P on a couple occasions....  They FEEL very good in my hand. The one I got to shoot was a smaller 40 cal and I did like it, but for my Glock I would have bought it on the spot...

The 45 is what I would get myself. (As no 10mm is offered)

CW

The .45 is my 2nd choice.  I guess I can see what making a 10mm barrel to fit the .45 M&P would cost and pick that up after my wallet recovers.

Anyone have any recommendations for barrel makers?