collision error on game . why ?

[mikesmith6486]

i have that shooting game with angles and velocity and collision detectio in it too . but it seems that it has some problems in it.
for example when i hit the target with an angle of 80 degrees and a power of 104, the bullet just goes through it and nothing happens ( but because i hit it something has to happen ! ) . but when i have the same angle ( 80 ) and now a power of 105, it its the target and detects collision and does the assigned event .
what's wrong with this !! it seems so weird and crazy ! please see the program along with its code and notify me what and where the error is and how can i fix it .
thank you very very much !

i have the file zipped .