One knob, which looks like metal to me, and two other parts which are not designed to be handled, General!
Why couldn't Sheila bash Nevill on the head with the rifle? You talk as if she was completely immobile, no weight lifting champion but i'm sure she could swing a rifle in a psychotic state surely? One unexpected blow and Nevill was out cold with a fractured skull. No problem whatsoever!
There's no way that little slip of a thing was capable of mustering the leverage and swing force required to render Nevil unconscious, not even taken unawares. Not a chance. Ever.
And that's also irrelevant anyway, as that's not what happened. In the life and death struggle across two floors and down the stairs, Nevil put up extreme resistance, despite being mortally wounded. Bamber used everything at his disposal to eventually subdue him and dispatch him, including using the butt of the rifle to batter him.
If Essex Police weren't so institutionally, criminally inept we wouldn't even be having this conversation.
'Yes, Jeremy, feel free to burn anything you like in the garden'.