Stebo, I bet he is looking at this one
Academy - Core 15 Base Direct .223/5.56 x 45mm NATO Semiautomatic Gas Rifle

From what I have read, the 3 groove polygonal rifling is only used on the piston rifles in the Core line up.

Boudin, I can't tell you anything about Core 15. Just another new AR manufacturer...only time will tell how good they are. With the Smith, you are getting a quality firearm with a reputable manufacturer standing behind it with customer service. As far as accuracy, or issues with the M&P, the new tactical model is basically a M&P 15 Sport, with the forward assist, dust cover, and quad rail added to it. Search this site or others for a whole bunch of reviews on the Sport, and you will see that the 15T should be a fine rifle. If you have any specific questions, let us know and I am sure someone on the board will answer.