So, just so I understand clearly, I'll tell you what I see here. If I'm wrong, correct me.
- Bow is an 'X' on the fingertips (Can be either one, but not both at once.). Each limb is 6 feet, and the intersect. (However, if they only protrude 2.5 feet in either direction from the center, then they would only be 5 feet total. So, is there a 1 foot diameter center?)
- Sending a pulse down the arm creates a concussive shock wave, which has a very limited range, and can be followed by an arrow.
OR
- Pulse that creates the shock wave on the primary (Right?) arm fires smaller, weaker arrows from the secondary (Left?) arm.
Now for the questions.
What does 13 KM mean? If it means Kilometers per minute, then that's pretty friggin' fast. It's roughly 2/3 the speed of sound. If it means they reach out to 13 kilometers, then that's pretty far, being that there isn't a hand held firearm capable of that distance in current existence. Otherwise, I actually have no idea what 'fire rapidly up to 13 KM' means.
What kind of damage to the arrows do? Piercing, impact, explosive. Is a direct hit going to run someone through, and take half their stomach with it to the wall behind them? Or is it going to shatter their skull on contact, without breaking the skin?
Explain the 2 foot shock wave a bit more. You state that it easily knocks people back. How far? Stumbling back, sliding back, or flying back? If released point blank, will it render the victim unconscious, not unlike a swift strike from a hammer?
Personally, I like the idea, but I feel that a few things need to be more defined.