Notice, however, how the only way to unlock it is to have already RECEIVED an ammo rack detonation. That is to say, you only get the 0% ammo rack detonation flag (which only lasts for 1 match before the flag expires, whether you use it or not) if you've already been destroyed by what's essentially the WoWs equivalent to a head shot.
On top of that, I have yet to get ammo racked myself so I don't know which it is, but you either get 10 or just 1 flag of that type, which is to say that it only can be used for 1 match or, at most, 10, regardless of what actually happens in the match. Given that First Blood gives you a considerable credit boost but you only get 1 flag, I would consider that the more likely scenario until I actually get this flag to confirm which it is.
Lastly, if you get ammo racked twice in a day, you don't get two of those flags, because you only become able to get more flags of a specific after a 24-hour period of getting that specific type of flag.
And lastly, remember that there are TWO ways to one-shot a ship: ammunition magazine detonation and boiler explosion. I'm not certain if the game mechanics count those differently, but the wording on the flag certainly doesn't mention boiler explosions.
They are, and it's because of the change in shell mechanics. AP now does 0 damage if it fails to penetrate, which makes AP far from the "Press 2 at the start of the game and then never think about shell types again" shell that it used to be for quite a while. Now we see what is properly termed an
"immunity zone," where at a particular range between two ships, AP rounds will do absolutely nothing because it will fail to penetrate the armor whether it hits the side or the deck, but WILL do at least some damage if the range is either increased or decreased. In this zone especially, and personally I do this when further out from this zone as well, use HE shells instead of AP. You can do amounts of damage with HE shells now that used to not be possible, if you use them in the proper situations.
Another interesting note regarding immunity zones, from a video Wargaming made about the Japanese warships: when attacking a Yamato, the Yamato will have the largest immunity zone of any ship in the game against you, while your own immunity zone will be at its smallest when fighting a Yamato. In other words, you'll find your AP shells dealing 0 damage against a Yamato at ranges where any other ship in the game would take damage, while you'll take damage from a Yamato at a range that, for other ships, would be an immunity zone for you.
