223 vs 5.56 cases ?

[JeepsAndGuns]

Lake City 5.56 cases are made of harder brass and not made thicker than .223 cases.

While reloading for several years, the above chart mimics what i have found. I always read about LC brass being thicker and less internal capacity, but measuring it and several other brands of brass, I have found it not true. In fact, the LC brass, (from what I have personally measured) has had the largest internal capacity. Now the same might not be true for other calibers.