[Retlaw]

Originally Posted by Neil

It's unlikely to be an air rifle with that penetration. Possibly a .22 rifle

From the size of the bolt & the magazine floor plate on those pictures, plus the effect on the target backing, it could be Winchester .276. Anyway we may find out if the plod ever get on the case.
Neil if that had been a .22 the silencer would have worked, and the shots would not have been heard, unless your thinking .22 varmit.