If you mean in war I'd say the .303 Brit.
If you mean guerrila/insurgent type stuff, maybe the 7.62x39.
Just guessing though.
Anyone know for sure?
During WW1 maybe 10 million people were killed. During WW2 50 million people were killed. Since the end of WW2 over 100 million people have died in various conflicts around the world.
Therefore a post-WW2 cartridge is likely to be the biggest killer and its probably the 7.62x39.
7.62x39.
all those insurgencies!
All those US and CDN Mercs using AK's because .223 suks and you can't trace kills