I've been using the Badger ccl for a bit now. it has the explosive rounds perk. I find it very useful as it staggers all enemies hit. it does a portion of the weapons damage as aoe (the explosion) on how much the damage is reduced is unclear as it does the same damage when I use other perks then explosive rounds. I find the the explosion does far more damage as if the targets arms and legs get hit by it they are damaged,each by about half damage to the actual hit. so that one shot just became 3 + stagger as for downsides it does make critical kills harder as the explosion might kill them instead of the actual shot. headshots are a bit more difficult but deal far more damage in my experience. as far as I can tell the explosive rounds perk on a scout rifle are really worth keeping. on a hand canon, not so much as it relies on critical kills.