The M240 is not a different version of the M249 SAW. The M240 is a .308/7.62mm medium machine gun that is a variant of the FN MAG 58 and L7A2. From what I have heard it is far more reliable under more adverse conditions then the M60, but I'm not sure which version of the M60 it was compared to. Not sure about the weights either.
http://www.remtek.com/arms/fn/mag/