I believe it doubles or increases your rate of fire. Double tap isnt really needed until you have a large magazine gun because if you use it with the MP40 which has not that much ammo, you will need to keep buying ammo for it every quarter of a round which will cost around 2000 points. Hope my info helped! [ Using it with raygun comes with good results!!! ]
You need to buy double tap root beer, which on the zombies map Kino Der Toten is located in the alley.
Quick revive, juggernog or juggernaut, Speed Cola, and Double tap.
Double tap basically makes your gun shoot faster just like in Call Of Duty World at War.
Double Tap Root Beer increases the rate of fire of your weapons.
it depend sif your playing black ops zombies or world at war zombies black op zombies has stamin up double tap and PhD flopper regular world at war zombies has speed cola jugger nog and quick revive
Zombies: Root Beer- Double Tap Speed Cola - faster reloading Quick Revive - Revive Allies Faster Jugg-Nog - More Health
juggernog, speed cola, quick revive, mule kick, double tap rootbeer, stamin up, phd flopper, deadshot,
Makes your weapons shoot faster and increses recoil if anyone wants to talk about black ops 1 black ops 2 or world at war i know all the secrets hacks glitches aand everything of them contact me at andregoodarzi@hotmail.com
If by soda machines you mean the four different perks you can use in Black Ops Zombies, you can get Juggernaut (Increase in health), Quick Revive (self explanatory), Sleight of Hand (Quick reload), and Double Tap (Quicker shooting).
I think it is
Tap the triggers on consoles and go to the terminal and type 3arc unlock...or bear campaign
All you have to do is double tap the down button on the Plus pad.