BDC ret's are set up in scopes to give common drop at ranges to particular cartridges loaded to factory speeds and BC's. They aren't perfect and some aren't even close. What all BDC customers have to do is take their rifles and ammunition that their rifle likes to the range and find where each drop line matches range. So yes you could use that BDC set up for .223 on your 7mm/08 rifle. You will just have to determine where each line relates to range which you would have had to do with a .223 anyway.