(adsbygoogle = window.adsbygoogle || []).push({}); These are just a few tips that hopefully will help you not run out of ammo and to keep your ammo for a long time.
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-HEADSHOTS

You do not want to get headshots during the first few rounds to maximize your points. But in further rounds, when points don't really matter as much as surviving, you'll want to aim at zombies' heads and upper chests. Zombies don't crouch or go prone so getting headshots shouldn't be too difficult. It should only take a few headshots to kill a zombie, so if there is only one zombie coming towards you just fire a burst of 3-4 bullets into their head, and if they don't die, try again. When you're facing a whole crowd, just fire in a straight line at their heads. It helps to have a powerful gun with large clips, like the upgraded HK21. The zombies will walk into your line of fire as they get closer to you. But WATCH YOUR BACK! It's not unlikely for a crawler to come up behind you and trap you.

-THUNDERGUN

If you are playing with friends, the person who takes the thundergun from the mystery box needs to be a very good player. Once they upgrade the thundergun to ZeusCannon, they should run around the stage in a loop to gather up zombies, and then blast them all with the ZeusCannon. This kills tons of zombies, but only takes 1 bullet from 1 gun. It really helps the team if one person is doing this.

-MP40

Every person should have the upgraded Ray Gun in the later rounds. It's hard to die while carrying one of them. Sadly, there is not too much max ammo in ray guns, so in late rounds, when you go a long time without a max ammo, you will run out of ammo. This is when you pull out your other gun. An upgraded LMG should last you a while, but if you upgraded an assault rifle, you will soon be out of ammo. When you are out of ammo with both guns, TRADE YOUR GUN THAT ISN'T THE RAY GUN*, whatever it is, for an MP40. MP40s are weak, yes, but they have a lot of ammo for a gun off the wall, and buying more ammo for it is cheap. Hopefully you can use an MP40 and survive until you find a max ammo.

Once you find a max ammo, you should hit the mystery box a few times and try to get a LMG.

*: Whoever has the ZeusCannon and the upgraded ray gun should be really careful and use their ammo slowly. If they run out of ammo, they should just run around the map with no ammo.

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That is what me and my friends do while playing zombies, and we can survive a long time without getting max ammos.

REMEMBER: Don't go crazy and shoot out all of your ammo when you get max ammo. Save it just like you would if you only had 10 bullets.

Good luck, and fun zombie-slaying =D

TBH, best way for kino and get atleast round 20 for me is:
Buy olympia straight away, knife for the first 2 rounds, then use the olympia up till about round 6, when you have that open the door thats up the stairs, swap the olympia or the m1911 for the mp40, swap the m1911 for the mp40 if you want to pap that, or swap the olympia for the mp40 if you want to pap the mp40 then just use the mp40 till you get to the next room, then the next room etc then turn power on and pap your guns when possible.. it works really well you get atleast 16 rounds even with noobs who have no idea

Only once on Der Riese, but it happened and that was the end of the game.

wow i might try that you might Own the zombies if your playing 2 player and get thundergun if you both know how to use it well

that exactly how i play my zombies, u made me think about it. all of all that works

Not bad.Not bad at all.