Hello again SS
I visited my local Halfords they did not have Carb cleaner so I got a can of Birchwood casey bore scrubber from ebay
and sprayed liberally into barrels and left to soak, eventually after an hour of hard cleaning and scrubbing the marks
have all dissapeared so obviously has been plastic or lead residue which has not came off when I was cleaning it out with WD40,
Many thanks for the correct advice I'm now very relieved to know I have not damaged my beloved miroku,
as I said I'm a total beginner and all these things have to be learned,,
Thanks again
R.P