Free floating is not about giving the barrel room to breathe, but to allow it to expand freely as it heats up without added stresses.

The problem is that hammer forged barrels (the cheapest, most common, and most flawed way of making a barrel) leaves all kinds of internal stresses in the barrel which cause 2 things- bad harmonics and uneven metal expansion/warping as the barrel heats up. Pressure bedding the front of the barrel dampnes the harmonics somewhat and prestresses the barrel and directs its expansion as it heats up. With a good barrel that has cut or button rifling or better yet, has been stresse relieved through cryo treatment, you absolutely want the barrel to be free floated. Since most factory rifles are made as cheaply as possible, they are pressure bedded by default. Its worthwhile to try to freefloat them, but there is a chance that this will hurt accuracy.