Id suggest just getting a couple of hundred round bulk packs of commercial .223 cases, and skip the military brass. The military stuff is more trouble than its worth, and its usually shorter lived.
A lot of times too, the once fired military stuff was shot out of MG's, which have more generous chambers, which can make sizing the brass more more of an issue.
The commercial stuff is a lot easier to work with. Lasts a good bit longer, no messing with primer pockets, annealing the necks, stuck cases, and you dont have to download it.
“The enemy is anybody who's going to get you killed, no matter which side he is on.”
― Joseph Heller, Catch-22