If you carry out an unofficial test fire of the rifle, silencer and control ammunition, on a date prior to the date when the official test fire of the same is carried out you run the risk of cleaning out any blood that may have originally lined the barrel of the rifle, and there is opportunity to produce a replacement bullet as part of the batch of crime scene ammunition, as appears to have occurred with bullet PV/20, which as of 7th August 1985 it was a fragmented bullet, but by 20th September 1985, it had become transformed into a whole bullet...