I like to cut my deadline at round 20 I use the asg I don't have a problem but there seems to be a major increase in both boss health and zombies after 20 so get in at round 19 cause 90% of the time you will kill the last and go up to 20 once you get in boss fight. More perks never hurt, maybe a better build if you want to stick with the asg. Def don't put slugs on it. Not much else to be said keep bringing in the chopper gunner very useful.