#16: bullet paths after striking walls and concrete are predictable. And follow the walls/pavement. Will post video later.
#5: Tactical swearing.
#2: the first through the door generally is fine, its #2 that takes the hit. OODA loop and reaction time.
#4: In Vietnam and Rhodesia it was fairly common to let the point men by, ambushing the main body of the group.
#15: depending on the op, single file on a path can be the most tactical, especially if you do not want the other side to know your numbers.