It has been my thought for some time that many people fret to much over cleaning AR type rifle barrels. Unfortunately, the "M&P Sport" doesn't appear to have a chrome lined bore (like a proper AR type weapon should), so copper fouling, rust, and barrel life will be much more of an issue than with a mil spec barrel.

The unlined barrel will need to be cleaned after every use to prevent rust. Copper will need periodic removal, but don't go overboard with it. I'd recommend "normal" cleanings with CLP and limited use of copper solvents. A bore snake is great for leaving a trace of CLP to help prevent rust.