BB Gun vs Cyclists - Hampshire

That would be quite some shot it has to be said.

A car travelling at 30 MPH would clear 400 meters in just under 30 seconds. In that time you would have to stop your bike, dismount it, adopt a suitable firing position (at the upper reaches of your range this would probably have to be prone), bring your weapon to bear, adjust for wind direction and bullet drop, (assuming that you are using a .308 this would be negligible but would have to be factored in nonetheless), work out how much to lead the target by, ensure that you are not putting any innocents in the firing line, check variables again, unsafe your weapon and then fire. Add to this the fact that your scope would probably need to re-zeroed what with all of the bumps / vibrations from carrying it on your bike, it would be a very impressive shot Mr Jackal. Hypothetically speaking of course.

Maybe but you would get to practise on water melons.