Round 19.
4 of us.
We stayed in first room until round 4-ish.
Then we moved on the thompson way.
Two people went off to get there guns and do teleports while me and the other dude stayed at mainframe waiting.
We got our guns and linked teleporters same sort of time.
We pretty much stayed there ages.
Once we upgraded our guns needed(mine were thompson and type-100)
The box move to the bowie knife teleporter bit.
We went up the the platform bit up here and camped.
1 at the window outside, 1 at stairs and two further down for backup.
The box moved.
We stayed.
I ran out of ammo.
Eventually the window and stair dude died.
They charged towards the trapped me and other dude.
He died.
I lied down and knifed the zombies legs.(I had juggernaut)
I died.
Everyone was having a laugh at how I was lying down knifing the zombies legs and surviving a while.(It was funny)

If I had bowie knife I may have survived it.

Round 21.

First get everyone to the box. then just farm points and hope for the best on the Random Box.
Hopefully have 2 people with PPSHs and one with Trenchgun and one with a weapon that is good SHORT - MED range the STG is good for this. when you have all the weapons you need camp up on the stairs above bowie knife, near the box but on the out side. Activate Power Etc.

Upgrade weapons as soon as possible. This is what my team of 4 had:

2x The Reaper
1x Gutshot
1x PTRS

The two with The Reapers stay at the top of the stairs facing the teleporter and the two with the others stay on the outside, cover the window and help thin out oncoming zombies. This spot is good because if overrun both teams have a quick drop off point and with monkey bombs this is even easyer as you can lure zombies into an open area so you can rack up points. If you become to overrun and one person is left, tele around from the room you are in and switch to the Tele rooms with the Type 100 and the MP40 you can just jump and switch if alone.

We got to Round 21 because we were after Achivements and went to do Elivate your Senses and Pack Addict and became our downfall. But this tech is good for getting rounds 30+ as the The Reapers have 700 + 100 Rounds and you can switch out on places on the stairs so the other team can farm points aswell.

My List of Weapons and Achivements for that game:

The Reaper
Spatz 447 +
The Imploder
G Compresser
Amargeddon
Acellarator
Impaller
C 3000

Achivements:

Pack Addict
The Might of the Monkey
40 Knives
Perk aholic Anon (perks are useless. upgraded guns is where it's at)
Freq Flyer
Elivate your Senses

So all in all. a great way of getting upto 30+ rounds.

PS. Two man team got to 20. No trouble but i had to go for dinner

I honestly think the strategy for this game is to keep teleporting. Upgrade you guns and make sure you have a light one. I made it 4 rounds by myself cause my teammates kept dying. I ran to the left teleporter, sprayed my MG till out of ammo, teleported, got that power up it gave me and went right and did the same thing. I kept moving left to right, left to right. My guns were Ray gun and MG, and I woul kill the 1 or 2 straglers with the Ray gun and then camped. This worked for me until I decided to go to the Bowie knife room, then he zombies split up and trapped me in. Otherwise I could have made it if I hadn't gone middle.

Round 26 btw. I was alone 22-26 8)

That tactic sounds beast Roadiie.
I'm gonna use it, thanks! 8)