Well if you want to be realistic, dont spawn a bullet. You cant see a bullet flying in real life so why would you in the game. Make an invisible laser for your carachter and:
If "laser" is overlaping(Enemy)
and Key(shoot) is pressed.
> Destroy enemy.
This way you can simulate high speed with pixel perfect collisions.
I didn't say I want to be realistic! I want to give the the player the illusion of bullet velocity. Anyway don't expect players to understand the frame rate technical crap.