MASTERMIND OF THE WEAPON X PROGRAM: The Professor can use Empower and Outwit with a range value of 8. When he does and counters a power on a character with a range value of 0, he may immediately Mind Control as a free action targeting that character with a ranged combat attack regardless of range, and takes no damage for using this Mind Control.

If I give the Sniper Rifle to Professor, does his range value still become 10 for Outwit or 8 because that's what is specified in his SP?

I think the sniper replaces the value first, then the power replaces the sniper value:

0->10->8

correct!