Negative,
They (mag and sporter) are both @.660 at the muzzle, the difference is the mag starts out at a greater diameter near the receiver (I want to say 'shank', but Remington doesn't have a traditional shank).
Anyways the mag is thicker at the shank and carries it out forward but ends up at about same muzzle diameter as the sporter.
Good description. It explains why I was able to put a mag contour and a spotter contour in the same stock.
