their is multiple factors that are involved, one of which was your shooting it is absolutely terrible, most of your shots actually missed but there was 2 rounds possibly 3 that hit him, their is also issues with the connection I will show you something that happened to me a while back with similar problems, i put enough bullets into someone to kill them 10 times over.
We have also been issued with a new vest which is armour 5 rated, similar to the UNMC but theirs gives slight better protection in the groin area.
their is multiple reason why he did not die but mostly it was your shooting.