Some guns will not shoot free floated, others shoot best free floated..the worst thing about free floating is the craze to hollow out the stock like a water trough as opposed to undercutting it IMHO, its a way to preclude the word inletting from ones vocabulary...
When I stock a rifle, I bed it tight first then if that doesn't work I 3 point bed it with contact at tang, recoil lug and one inch of barrel and pressure at the tip..then if that doesn't work I free float it..that way you don't have to put the wood back in the stock as that can be a very difficult stunt indeed....there are no positives in bedding but generally speaking I believe most featherweight barrels tend to shoot best with the 3 point bedding, maybe...bull barrels are not very particular and shoot well bedded tight, 3 point or free floated or so it seems...but each rifle is an inity unto itself..
Anytime something touches the barrel that can change the pressure applied to it due to screws loosening or stock swelling, shrinking or shifting etc. will constantly change the harmonics and can cause bullet impact change. Bipods can affect this too if not floated. Your choice.
A good custom barrel w/#2 contour up usually benefits from free floating. Factory hammer-forged barrels usually benefit from a pressure point as do the pencil contours in custom barrels. Like the other posters said every barrel is individual in itself. On a free-floated barrel in a McMillan stock I like about .040" clearance w/#4 contour barrels. It aids in cooling and you never know what kind of improvised rest you might be shooting from in the field which could stress the forearm. sure-shot
