My P14 barrels are just like that, terrible at fouling, but good (well as good as my eyes are) at grouping - don't panic, enjoy your new lady, she's grand as she is! If you could find a good period scope & mount, perhaps a Griffin & Howe type then I'd use them.
Nothing 'new' as this would dress this old lady like 'lamb' when she is most definitely not!
Fantastic rifle by the way matey, its a corker!