there should be a option were when you are in the pawn shop you can have your wepons modified for a price kind of like a gunsmith that works with every thing
a sigestion for the new rebuild one would be when you complete one game and they send you to a new map make it so the survivers for the old map talk to the new colony maybe send new wepons
 "The Last Stand 2"){kind=icon}
 "Top Shot: The Game"){kind=icon}
 "Rebuild 2"){kind=icon}
 "The Last Stand: Union City"){kind=icon}
 "Boom Town"){kind=icon}
 "Warfare: 1917"){kind=icon}
 "alien exterminator"){kind=icon}
 "Custom Gun Maker 2"){kind=icon}
 "Decision"){kind=icon}
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 "Autumn War"){kind=icon}
 "Special Forces Training"){kind=icon}