I would recommend the getting the rifle with both the scope and silencer (Way Easier). There are 3 scopes 1-4x , 4-8x, and 8-16x . Once you have your gear which you will find on the first island (hunters house rifle and scope 1-4x) you start on in the game you can go back a redo towns and houses you already cleared out along the way as the dog machines respawn again there over time. With this rifle you can ONE SHOT KILL the dog machines with a shot to the energy pack at the top of their backs. Some dogs do not have an energy pack on their back for some reason so heads up and the head shot can be good or fail sometimes. The dog machines are the best kills for the rifle (forget the hunter he will DESTROY you if all you have is this rifle) . The flying sentry bots work as well with a head shot but that is sometimes hit and miss too, the battery pack on the dog machines ALWAYS works.