Word of advice on kannon. Dont zoom in. If you learn how enemies tend to and where they shoot from or defend from you can fire the gun blind pretty easily and score lots of kills. Dont bother with ard or eavy armor and use an ammo refill. Then you can just blast away happily for a long time. Lets face it if someone finds you the armor doesnt make a difference so it is better to enhance your offense capability than your survivability.

It took me -ages- go gets all da bitz togeva to make dis 'ere armer. 'pose it's best off goin to da skarboyz.

Also try aiming the cross hair so that the lower bar is just barely touching the top of your targets head for really long shots. If you miss you can drop it a little and they probably dont know how close they came to dying.