It's not that hard if you think about it

Just have one reward at 7 kills..the Harrier Strike. That usually gets you three or four, which gets you to the other reward at 11, the Chopper Gunner. If it's a big open map that can easily get you 15 kills. Before you know if you have 25 and a nuke!

But I haven't even put it as a reward yet. I've had two plus 25 kills though.