This is easiest done while playing as Nisha the Lawbringer, as her Showdown skill will allow you to lock on to enemies automatically, saving you the frustration of missing the shot after doing your 360 spin. You can get her action skill as low as level 3.
Also, when you start the game as Nisha you will have a sniper rifle and a pistol, meaning you have many chances at this achievement from the very beginning. When you get to Elpis this achievement will be even easier with the low gravity/Oz kit.