Federal, but that's why it's the WORST. Virtually all 5.56/.223 brass is fine for reloading, except for Federal (and not counting "Federal" [really Lake City] XM193).
Federal brass, as found in American Eagle and Federal Premium, has a case head that's only 50-75% as thick as it should be. This substantially weakens the brass, and allows the primer pocket to open up even with mild loads, resulting in loose or even lost primers. I had several pieces of twice-fired brass that not only lost the primers the second time, but wouldn't hold a new one; they'd fall right out.
In order to compenstate for this, Federal brass has thick sidewalls, which reduces case capacity and increases pressures with the same powder charge compared to any other brass. If you weigh it, you'll find it's a lot heavier than other brass. Federal also loads these rounds light, because their brass isn't up to high pressure loads.
I tell everyone to junk this stuff; pretend it's Berdan-primed and trash it.
Again, the Lake City brass used in "Federal" XM193 is great, because it's made to military specs at the Lake City plant, and not in Federal's Minnesota plant.
I've used the following 5.56 brass for reloading with no problems, and they're all close enough that you can consider them the same:
- Lake City (and other military brass, like TW)
- IMI/TZ/TZZ (Israel)
- PMP/DNL (South African)
- IVI (Canadian)
- Mal (Malaysian)
- PMC (Korean or South African)
- S&B (Czech)
- CJ (Chinese/Norinco)