This is similar to what the defence would create. In my view. Either in private or for the trial.
As it matches the crime scene. There were no claims of the police moving things pre crime scene photos then. Or of the silencer not being used.
A possibility Sheila went downstairs to re load after shooting June & Nevill. Once she had returned upstairs into the twins room, Nevill went downstairs to start phoning Jeremy. This would have given Jeremy less time to answer.