Fluting the barrel just to save 100g is probably not worth it. As part of the whole package that vietnamcam mentioned (and don't forget lightweight firing pin if a rem 700) the total weight saving can make quite a difference, but only you can decide if it is worth it. In my experience a carbon fibre stock will save approx half a pound (200g?) over a typical factory plastic stock and nearly a pound (400g) over a wooden stock.
I went down this route with my model 7 and and saved nearly 2 pound all up, but most of this came from the stock, I would say the normal saving would be about a pound, but will cost about a $1000 all up.
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