Yes there is - it's called the Geneva Convention and the signatories have to use 'full metal jacketed' ammunition so that it doesn't 'mushroom' on impact.
The Russians got around that with their 5.54mm round: it has a hollow nose cavity under the jacket. Looks like a solid, ball round, but the thin gilding collapses and it acts like a hollowpoint after impact.
The Russians appear to have mostly given up on the 5.45mm round for now and continue to issue 7.62x39 for their domestic forces. 5.45 now appears to be limited to SMG-type use.
I understand it is a very nasty round, wound wise.
Isn't the SS109 round designed to break into 3 parts? But the velocity has to be up around 2800fps.
The short barrels on the M4 reduce the range that that velocity can be maintained. Less than 100 yds.
The longer barreled M16 16-20") increase the lethal range.
Think that's what I've read.