The barrel is melonite treated. Gives a hardness comparable to chrome, but does not change the dimensions of the barrel, so it is inherently more accurate than chrome lining. The barrel has a 1:8 twist, which I like because I shoot mostly 55 grain, but it will handle up to 75 grain. It also has 5R rifling, which many target rifles are using now. Gives a better gas seal and higher velocity.
Smith got the 5R rifling capability when it acquired Thompson Center. It was already using the melonite treatment for the M&P pistol slides. Its website indicates that it can produce the melonite treated 5R rifled barrels for less cost than a chrome lined 6R rifled barrel and provide a wear resistant, corrosion resistant barrel that is more accurate than the standard chrome lined barrel in most AR's.
I bought a Sport a few weeks ago after much research. Three range trips and I'm very pleased. Haven't needed the forward assist yet.