User blog comment:Callofduty4/Modern Warfare 3 Weapon Proficiency and Equipment trailer/@comment-1902548-20111028200120/@comment-24.179.45.23-20111028225032

Dropoff means that it will maintain its close-up damage over a longer distance, range means that the bullets dissappear further away (only shotties have bullets that dissapear. Quite innacurate).