With reloads I have seen signs of excessive pressure with loads that should be well below mazimum and now that I think of it it was military 5.56 brass.
If the military brass has less internal capacity, it will take less of a given powder to reach a specific pressure than commercial .223. Chamber specs vary a bit between 5.56 and .223, and even the Wylde chamber. The cartridges, loaded to their respective pressures are interchangeable, the minute differences in chamber specs for reliability.