Military brass is typically harder than commercial brass; it's never been intended to be reloaded. It's also less uniform than commercial brass. But it's cheap and may well suit the needs of many folks.
Regarding max pressure specs for the .223 and 5.56 rounds, the NATO version has the same max pressure specs as the .30-06 and its siblings of different calibers; .25-06, .270, etc. Ditto for the .308 Win. and it's sub caliber siblings. The .223 commercial version has lower pressure specs by about 10%. Several 22 caliber centerfire cartridges have the same pressure specs as the 5.56 NATO round. Therefore, the .223 Rem. has lower pressure specs than most modern cartridges.
Last edited by Bart B.; October 3, 2012 at 09:30 AM.