Free floating barrels improves accuracy in some rifles, but far from all. It is dependent upon barrel shape and dimensions, as well as the rigidity of the action. From a military perspective, free floating requires a rifle design that retains its overall strength from components other than the barrel, for example the AR15 system with a strong fore-end (which is still a mite fragile). Mounting bayonets, grenade launchers, etc. all affect the barrel resonance and affect accuracy. The military need a rifle that is primarily reliable and sturdy before accuracy is an issue. Precise, pinpoint accuracy is not attainable under combat conditions. Only sniper rifles have the need for such performance and they are designed accordingly.