I'm guessing its in Scotland?? Edit just seen Scotland mentioned in the title
Good question and possibly different for all 4 countries, possibly even regional variations but wether legal or just local policy
Did the foreshore not change hands like everything else crown wise has done to holyrood a few years ago, probably longer ago now.
For shotguns u need to below high tide mark, if u did that with a rifle would it not make a very flat shooting ground, unless u had ground adjoining it to shoot downhill onto it ( assuming it is legal)
Must admit not a wildfowler so not 100% on exact legalities esp since it changed hands and out off season.
Also things are far more regulated in recent years with access and club grounds or NNR, u used to be able to shoot almost anywhere without being a club member/day ticket holder, now far more like English system
But if it was a free for all u could rock up at beech with ur clay traps every Sunday, obviously with non toxic shot and bio clays.