If a 'gun' is supplied by the police, the calibration certification ought to be in order so that officers can also use the device!Yep two of my friends were in the Speedwatch scheme in their Surrey village. They had some basic training on using the 'gun' but I don't think it had the normal schedule of calibration/certification so although the data from it was probably fine it wouldn't have stood up in court. This was 15+ years ago ... IIRC they were only allowed to operate in 30 or 40 mph zones.
Certainly in my area volunteers are not allowed to operate on 'fast' (national speed limit) roads.