I have been amazed that the marketing arm of S&W has not figured out that there is a market for a 22 conversion unit for the M&P line. If they were smart they would contract with Tactical Solutions to put out a really first class 22 conversion unit for their M&P's.
I have 6 conversion units for the 1911's - 2 Marvels, Jarvis, Tactical Solutions, Ciener and original Colt. I also have both the Ciener and AA units for the Glock 17.