Ever since I got my first S&W M&P, I have been after a threaded barrel for it. I finally got my account setup with Storm Lake and picked up some of their threaded 9mm barrels. I got the barrels threaded in 1/2X28 as this is one of the more common thread pitches for suppressors.
Storm Lake advised me that I would see better groups out of their barrel and I would have to say they are right. The gun is shooting tighter groups.
I am using the AAC Evolution and running 147gr Sub Sonic ammo through it without a hitch. No malfunctions at all. :D