Ok, so I can honestly say I know for 100% sure that you must kill 5 opponents by bouncing the bullets off of a surface with the scatter gun to get the achievement. I am completely sure about this because I must have killed 100 enemies with the scatter gun by hitting them straight on, and I did not get the achievement. But then i tried bouncing the bullets off of the ground and into the enemies, and WHAM achievement unlocked. No offence Pants Party but your mistaken on your guide on that achievement. So the description is actually correct. So for anyone going for this achievement, save your self alot of frustration and bouce your bullets.