On another topic, Hellbender from the OWS clan had said to fire in controlled bursts, and aim for the head. I need to take note on this too...
Actually with weapons such as KF7 or AR33: aim for the chest/neck, it's usually 2 hits to the chest and one to the head and if I remember right you only need 3 bullets to kill someone with an AR33 by using this technic.
Once you know where the middle of your screen is, the technic can succeed pretty much all the time.
Same goes with our lovely Moonraker laser. When I was playing, many people were complaining that I was killing them in only one shot with my Moonraker laser, just because the weapon is very accurate and I was hitting them in the head all the time, where ever they were.
And again... same goes with the Bishop, it's a very, very, very good weapons if your aim is good.
To kill someone quickly with the Bishop, you've got to hit the player in the head every time you shoot. The way to do it without losing accuracy is to "shoot, hold your fire for a second, shoot, hold your fire for a second, etc..."
PP7 can be deadly as well, just use the same technic as the Bishop.
But first thing you've got to learn is: NEVER stand still and avoid using the crosshair else you're screwed.
I hope this helps.