How much is the M&P Sport?
I put together a kit from Palmetto State Armory for less than $700 ..... Upper reciever had the barrel already installed, so the rest of it was really simple stuff.
http://palmettostatearmory.com/index...ifle-kits.html
http://palmettostatearmory.com/index...receivers.html
Items are often out of stock, but don't stay that way very long....