Prestige
When you have reached the prestige level (after level 55), there is a very easy way to level back up again to 55. Focus on getting all of the "marksmen" challenges for each gun individually. These are worth massive amounts of points. Some other challenges to focus on for example are the vadalism challenges. All you have to do is throw grenades at the cars and you will get an easy 250 points. By doing this, you will be able to level up faster.
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