You probably have to assure that the 'you' isn't empty.

Other suggestions:
- you could start the scan a few moments later, when the bullet already left the gun.
- Did you try IGNORE_YOU? Although, it has to reset after leaving the gun.
- you could scan from a position ahead the bullet:
vec_for_angle(temp, my.pan);//Get a 'direction' from the angle
//Now, when the position is one quant ahead the bullet, scale the vector/direction to get the position a few quants more ahead, let's say 10:
vec_scale(temp, 10);