Unbreakable Vow Truly Unbreakable

[lealess]

No: HPFGUIDX 138843

It occurred to me that the Unbreakable Vow might function separate
from the will of the person making the vow, i.e., that taking the Vow
sets a certain course of action in motion.  This would be similar to
firing a gun at someone: even if the person firing the gun changes his
mind after firing it, there is no way he can alter the course of the
bullet.  So, when Snape promised to fulfill the third part of Draco's
task upon Draco's failure, the bullet left the gun and Dumbledore was
effectively dead, either at Snape's hand or at Draco's, unless both of
them were eliminated.  The Vow itself would eliminate further choice
on Snape's part, even if he did not know what he was vowing to do. 
The Vow would assume agency, acting as a sort of Imperius Curse,
supplanting the will of the person who made it.

Possible?

lealess