When the Magic Shortbow was first released, the special attack only used 35% of the player's special attack energy. This allowed for two quick shots, that—with enough luck—could allow a player to one-shot another player. This was said to be too "powerful", and Jagex changed it to the current 55% special attack usage.
Can you faggots above (Old English, Blackmamba, Pure nitros) not post shit if you don't know the answer? And OP seriously you could have found this with a 2 second google search