depends on how old it is , all of the 336' s that i know of have been drilled and tapped for a scope at the factory but , like i said it depends on the age of it , to determine that you should try to contact the maker ( marlin ) and give them the serial number and they should be able to tell you . what is the exact model designation buddy ? 336 cs , 336 sc , 336 t , you should be able to get screws to replace them from the marlin factory but , try your local gun smith first , i' m sure he' d have some .
