"According" to S&W the 15 22 ALREADY has a match grade precision barrel. This has been disputed, some people on this site, but as I say S&W lists it as such. Its # 10 on the list Here is the link to the info.
M&P15-22<br>.22 LR - Smith & Wesson
M&P15-22
The M&P15 rifle line has expanded to now include the new M&P15-22. Chambered in .22LR, the M&P15-22 rifle is built with high strength polymer upper and lower receivers. This creates a reduced weight rifle that retains the looks and operating features of the standard M&P rifle.
1. 6 Position Collapsible Stock
2. Functioning Charging Handle
3. Adjustable Rear and Front Sights
4. Two-Position Receiver Mounted Safety Selector
5. Cartridge Case Deflector
6. Bolt Catch
7. Recessed Magazine Release Button
8. High Strength Polymer Magazine
9. Light Weight, High Strength Polymer Quad Rail Handguard
10. Match Grade Precision Barrel