Very simple tutorial. Copy _zombiemode_spawner to yourmap\maps folder. Open it in notepad. Search for zombie_gib_on_damage() function. Should be located around line 1523 You should see this about 9 lines into the function Place this just before that Bullets should now do double damage after purchasing/obtaining double tap. It's not exactly the same as the DT2.0 from BO2 but it get's the same job done. Double damage. This can also be made into it's own stopping power perk if you want, but I leave that up to you.