[Tony O]

I thought it had to have full a metal jacket to be a legal military round.

[Joe 6-pack]

"I thought it had to have full a metal jacket to be a legal military round."

It just has to be designed in such a manner as to not inflict superfluous injury in order to be used against uniformed combatants. The round pictured looks like an M855A1, which certainly fills the requirement.

Back in 1990, the Army Jag Corps approved the use of the M852 7.62x51 match grade boattail hollowpoint for use by Army snipers. The memorandum I linked to explains the rationale in light of the text of the Hague Convention language.