Military 5.56x45mm Ammo is very very hard on .223 Barrel throats and will erode them. 
Your CZ Rifle is chambered for Commercial .223 Ammunition and that is what you should use in it.
I don't know that "
very hard" is correct.
There are two issues at hand here:
1. Military weapon chamber specifications call for a longer leade (throat) than commercial specifications.
2. The NATO specification for maximum pressure for the 5.56x45 is significantly higher than that of the 223 Remington.
Neither of these factors, either separately or together, would lead to the conclusion that 5.56x45 necessarily contributes to rapid leade deterioration. Leade deterioration is caused when hot gases cut the metal in the barrel in the area immediately in front of the case mouth. All ammunition causes this to some degree. The factors that cause leade deterioration are the combination of temperature and pressure. Relative high temperature plus relative high pressure cause more rapid erosion than relative low temperature plus relative low pressure, or high temperature plus low pressure, or low temperature plus high pressure. Temperature is largely decided by the chemical makeup of the propellant, while pressure is decided by many things, including quantity of propellant, length of leade, thickness of the case, etc.
One other issue that figures into the mix is that even though NATO specifications allow for 5.56x45 to be loaded to almost 20K PSI higher pressure than the specification for 223 Rem (62K vs 55K PSI), that does not necessarily mean that all NATO ammo is loaded to that level. In fact, the small amount of unscientific study that I have done over chronographs indicates that that they don't. More often than not, the US military ammo that I have shot over the chronograph indicate that the military version is often loaded
below 223 Remington commercial specs, since in several instances, I have seen lower velocities (120 - 80 FPS lower) in the milspec ammo from the Lake City plant that Remington Core Lokt for the same bullet weight. In general, physics dictates that lower velocities are indicative of lower maximum mean pressure. I don't shoot a whole lot of factory ammo, and it may be that I stumbled on the only two anomalous batches.
All this is to say, that, you
may suffer negative side effects by using 5.56x45 in a gun chambered for 223 Remington. And, you may not. My advice would be to use the correct ammo for the chamber in the gun. Always take the side of safety when dealing with tens of thousands of pounds of pressure.
