The guy that built my .300 mag for me hand-cuts all his own barrels.
Back in 1998 when I ordered my rifle, he would NOT flute the barrel. He said that the extra-machining done when you flute the barrel stresses the steel in places, and it does impact accuracy. If you want the most accurate gun you can get, do not flute the barrel. Heavier barrels help, but the two the single-most important factors for accuracy are having a good, smooth straight barrel to start with, and making sure the barrel has a good crown on the end.
I wouldn't flute the barrel, for cooling, get a heavier bull barrel and don't flute it.