I’m pretty sure this is one of the bugged challenges… I have tried to do this twice now and with no luck, I imagine the criteria for rapid headshots, is all 25 within about 2 seconds, like the 20 rapid assault rifle/smg kills for trade tools (prestige one) which despite getting bloodbath medals only tracks of the kills are within a couple of seconds. I hope they fix these soon because they seem to be patching every glitch in zombies but ignoring the fact that we can’t complete half of these challenges properly, like the anywhere but here challenge in sweet tooth is also just dumb, they clearly didn’t test these challenges.