I've tried to solve this through reviewing docs but the GDscript page on the master doc still says I'm typing this correctly.
I've dragged and dropped my chosen scene as well as right-click loaded it from the export section of the node properties.
Export (PackedScene) var bullet
> print(bullet) #returns Null
Exported property editor displays my chosen scene "Bullet.tscn" as well as it's image.
Attempts to apply "bullet.instance()" cause error "Nonexistant function 'instance' in base: 'Nil'."
This is an exact port of functioning code from the stable version of Godot.
EDIT: Solved, Scene from Player.tscn was not in export section of Main.tscn.