First we are talking about Arran not Scarborough.
I spent two nights there and paid £18.
Second the campsite at Lochranza is privately owned the council have no facilities there for chemical waste and to date the owner is not willing to allow wild campers to use them for a fee as they do on mull.
My suggestion is to either attempt to encourage the owner to open his waste point for wild campers or if they are not willing to install their own. If you read the letter from the council you would be aware that the reason some parts of the island have not already installed waste points is due to the fact that they are not connected to sewage systems and use septic tanks. I don’t know what you mean by installing something that is already there, for wild campers currently at Lochranza there are no facilities.
Third not all waste from cassettes is harmful to septic tanks which are used primarily on Arran, I was merely attempting to highlight that Motorhomes equipped with SOG systems, or who use green chemicals will not damage septic tanks. I can see no harm in this whatsoever. It may be possible to prohibit the use of blue chemicals on the island. This information could be given when booking the ferry and possibly on arrival homers could be asked to show what chemicals they are using.
But I still do t know what you mean by ammunition.