During. The gun starts to recoil as soon as it goes off.
This, by the way, is why heavier bullets hit higher.
First, heavier bullets recoil more, so the muzzle is higher when the bullet exits.
Second, heavier bullets are slower, so they are in the barrel longer, allowing for even MORE muzzle rise before exiting.
If you have a fixed sight gun that shoots low, change to a heavier bullet load, and watch point of impact rise.