Originally Posted by Snowed
To better answer this question:
If you're using an insta kill modded weapon, and one (a shotgun) that can do the round skip glitch, it only takes about an hour and 10 minutes to complete all 10 rounds by yourself. More players who are competent will obviously make this go faster. I got one of mine done in 45 minutes with two other people, one using modded weapons.
Care to elaborate more on this round skip glitch?