The latest military 5.56 rounds are actually steel, and designed for penetration, not fragmentation.
The US army is now using M855A1(Steel core, and steel penetrating tip), which replaces the M855(jacketed steel core) What you are thinking of is the 1899 Hague Convention, not the Geneva convention. Also, the USA was not a signing country.
https://www.army.mil/article/41283/army_begins_shipping_impr...
