The bug, which has remained undiscovered since launch, may explain some of BF4's "odd" behavior.
Have you ever been playing Battlefield 4, had a tank shot perfectly lined up, and then just had it miss for no reason? How about having your under-slung grenades flung back at you despite shooting them into open space? What most people previously attributed to lag may actually be due to the newly discovered "death shield" bug.
Basically, when a player "dies", there is a short window of time in which he can be revived by a medic. These downed soldiers extend a sort of invisible wall from their "corpses", which blocks, and reflects all incoming projectiles. That means, say, if you kill someone with a tank, and try to shoot at something directly behind him, your tank shot will always miss.
When a player is fully dead (as in, the revive window has closed), explosives and projections will pass over them fine, but in this pre-death downed state, it seems the game is misreporting hit boxes, causing the invisible wall. This bug is most noticeable in the closed-quarters maps of Operation Metro and Operation Locker.
This bug is quite a large, game-breaking one, and it's a shock that it has remained undiscovered until now. EA and DICE have had their hands full with Battlefield 4 bugs right from the get-go, going so far as to halt work on DLC until it fixed all the bugs (although, with some updates, they introduce more bugs than they fixed...)
Despite these glaring issues with the game, EA still insists that the game "was ready" when it launched last year.
At least now I have something to blame for my abyssal accuracy ratio.
Source: PC Gamer