I am slowly rebuilding a ball catch Mk3 Meteor, bought as spares last year. Bearing in mind that it is 50+ years old so may have worn and is just the assembled barrel and cylinder, the lock up feels weaker and it is much easier to break open.
It won't be as well engineered as the Feinwerkbau and this was obviously a short lived experiment which BSA must have revoked for a good reason.
Still looking for a stock for it.