It takes less delta-v to eject him from the solar system completely than to drop him into the sun.
The Sun is also surprisingly easy to miss, because
A.) it's a relatively small target (compared to the rest of the universe) and
B.) constantly releases a solar wind that pushes projectiles and rockets off course and gets stronger as you approach it.
It's like trying to throw a scrunched-up tissue paper at a fan.
So if you shoot a projectile at Sol, it's probably going to miss and end up in an orbit around the Sun or Earth, which means it will eventually end up back where it started.