This last episode before the 'Southland' season finale felt like a bit of a placeholder. Yes, there was a shootout, and Ben got in John's face telling him flat out, "You have a problem," but you know they're holding the big stuff for next week's season ender.
'Failure Drill,' the episode title, was explained on the police shooting range where Lydia had gone to brush up on her skills.
Another officer explained it's a sequence of shots -- "two to the body, one to the head" -- designed to bring down a suspect. If the first two shots don't drop the suspect, he's wearing a vest and you've got to take him out with a head shot, advice that Lydia employed before the episode's end.