All "free-floating" means is that there is no contact between the barrel and the wood. This is easily checked by sliding a dollar bill or a business card from the front of the stock back to the rear of the channel.
When it's free-floated, there is no change in the pressure on the barrel as it heats up during a string of shots. Free-floating also lessens or eliminates changes in pressure on the barrel from any warping of a wood stock from changes in humidity.
Some barrels, when free-floated, do not vibrate exactly the same from shot to shot during a string. I have no idea why this is; it just "is". (Ask WJC)
What I have found to be effective over the last 50 years is to take a 3/4" to 1" strip of kitchen wax paper and fold it back and forth until this "shim" is thick enough to require a five-pound pull between the forearm and barrel to get it in place at the front of the forearm. It acts like a shock absorber on a car--sorta--and dampens barrel vibrations. It has improved the accuracy of a bunch of my rifles, over box-stock original. Cheap, too.
Hope this helps,
Art