1. Move toward enemy. He will have 99.9% chance of shooting you.
2. Aim your move cursor over his body.
3. Push the finger down on the left mouse button and it'll shoot the gun.
4. Watch how the enemy takes damage.
6. Have a crumpet.
Its hard to believe that you cant get kills with that weapon. I have it perm and it is the only gun I use. But the best way to use it is with speed gear and just spray. But not like a noob spray like an accurate spray.