"Following the path immediately will be a problem because the bullet will have flown past the path start the next tick.."
Yes I think this is the problem, this is a kind of example to which I can explain what I am looking for:
Imagine a track with a car driving down the main straight then the car comes into view from the left side of layout with the bullet speed set to 35, the player then places their finger on the car to initiate the path drawing function and proceeds to draw a path for it to follow anywhere on the layout for it to follow.
I hope that gives you a kind of better picture of what im trying to achieve.
Again thank you for your patience and help with this, much appreciated.