You're browsing the GameFAQs Message Boards as a guest. Sign Up for free (or Log In if you already have an account) to be able to post messages, change how messages are displayed, and view media in posts.
It's a one kill streak. Basically, it's great if you want to troll cause dudes rage but it's worthless really.
I wouldn't call it worthless, it's basically a guaranteed kill, sometimes a double kill. Plus, for some reason Flak Jacket is useless against Hunter Killers. But on the flipside, a RCXD won't kill a FJ user when you explode it right underneath them.