I would guess... the "Black" might not be sealed at the neck and primer ? Also, most likely the T1 bullet vs the T2 bullet.
from the TAP .223 75gr description...
Powder: Temperature stable with flash retardant
•Primer: Small rifle, Staked primer pocket
Also... IMHO, 75gr Hornady Steel Match is a great deal for that 75gr bullet.
$19 dollars / 50 rds... granted steel case, but....