Every time I've gotten a Nuke I've used: Predator Missile, Chopper Gunner, Nuke. Chopper Gunner is the ticket. Majority of the time, the chopper gunner takes me to my Nuke.
So 5 kills to Predator, I get usually a double with the predator so that puts me at 7. All I need is 4 more legit kills and I have my chopper gunner which (unless I'm on a bad map) will take me to my nuke.
So with that method, 8-10 kills to Nuke. That's the best way IMO.