A good ork list against necrons?

This guy Andrew that has just started 40k has played me twice in a 500 point game with necrons and won, I realize now that my lists before weren't the best against necrons but I think this list may do it, if not help me out some.

By the way he uses somthing like 2 squads of warriors and a lord with a res orb


HQ: big mek with kusom forcefield - 85

TROOPS: 9 boyz with nob w/ big choppa - 75
9 boyz with nob - 70

HEAVY SUPPORT: 3 killa kanz with grotzookas - 135
3 killa kanz with grotzookas - 135

Ah.

Well, you're trying to win a shooting war with Necrons, but your squads are tiny, and your support vehicles are relatively fragile.

I recommend big large chunky units of shoota boys. Just march up, blast away as you go, and assault when you get close.

Big Mek + KFF (85)

28 Shootaboyz with Nob with Powerklaw (203)
28 Shootaboyz with Nob with Powerklaw (203)

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This sounds win

Yeah pretty much just bring lots of boyz, they are only Necrons after all.