i don't know if i'm right but souls of purgatory are like cartouche for God-castiel...but this weopons gonna empty after god-cass'll killing all his enemies in heaven?

maybe i misunderstood...but it seemed that castiel needed souls to arm his weapon and killed raphael...so each time he killed ou gonna kill someone he Lost cartrigde, his weapon will ended to be empty?...am i right ou wrong? am i misunderstood something in the explanations of 6th season?