Uh, my CoD experience? What CoD experience?
Wait, do the zombies have guns, or just shamble around?
And are these old fashioned zombies, or rage-virus zombies?
Well, I'm substituting my S.T.A.L.K.E.R. Call of Pripyat Complete Pack (mod) experience, since the zombies shamble, and have guns, but don't aim very well.
I would choose the FN FAL, for its high precision, and bolt hold-open feature. [That means you have a faster reload because you don't have to pull a cocking lever]
If you disqualify the FN FAL, or my choice of zombies, then I'll go with a revolver or a war hammer.