I don't have an M&P so thanks for the measurements!

The versatility of these pistols encouraged me to try.

I converted new barrels so the "bark and bite" of the first few rounds seemed a little hot.
I should try it with a worn in barrel, but it's a lot of cutting the entire length of the chamber.
It's not like lengthening a 40s&w chamber to 10mm.
That's only around 1/8" of cutting.

Good luck and keep me posted on the progress!

John