This is an oft repeated myth based on hearsay, and conjecture, that has in fact, been debunked in this thread and others - see my post on this topic. While this is true for 308, it is NOT true for 223 - LC are not materially and consistently any less volume than commercial. In fact the opposite may be true in many cases: see the chart and look for LC06 - they held the most.
Thanks for stating that. I saw at least two posts on this thread about military brass vs. commercial brass thickness that were based on urban legend.
An just to reiterate, here's a chart: