"How To" Projectile 180° Smooth Rotation

Hi Guys !

I’d like to get your opinion about the appropriate way to make my projectile “who move to the left” make a 180° rotation and then move to the right of course in a smooth way.
I thinking using “velocity follow rotation” but i’m not sure it’s good way.

Thanks for your help

Kinda something like this.

EDIT I know there is no movement attached.

Narg