Is there a site or a formula out there for dry fire range. For example: I'm 13' away from my wall and I would like a scale target say at 400 yards a 6" target then at 800 yards a 12" target then at 1200 yards a 24" target and so on or what ever size at what ever range. I would like to make ranges and exercises to shoot in my basement this winter. Any help or ideas would be appreciated. Thanks everyone.