Found a spot where zombies can't hit you at all by PaP all you do is run up the hill and hold whatever key to keep going up the hill and they can't get you sometime you'll slide down but you could use this to get to super high rounds.

http://prntscr.com/f5v6zk
Other side http://prntscr.com/f5vbs1
On top of a barrel by the R870 http://prntscr.com/f5vbzz
On top of the m16 http://prntscr.com/f5vc72