Bamber was crouched/kneeling holding the rifle horizontal, level with the mattress side(s), and pointing at Sheila who was sitting upright. The first shot tracks straight through her neck to fracture the fourth vertebra. The shell casing hits the mattress side (maybe the bedside cabinet as well) and bounces off landing on her right-side (DRH1). Sheila falls back. Bamber, still crouched fires again, this time with the rifle nearly parallel with her body so that the bullet travels directly into the brain. Shell casing again hits the mattress side but is cushioned more than the first and lands in the corner on Sheila's left-side (DRH2).
I rest my case. 
Not at all: one of the theories I put forward was that the gun could have been on its side to be comfortable to fire - as it is in the photographs. Then the casings would have ejected up into the air and down. If he was staging it and she was co-operating I don't think he'd have her on the floor by the bed, he'd have her by June or in the bed, or in her own bed. The place she was found was too odd for a staged murder, but had the randomness of spontaneity and fits with the fact that bible lived in that bedside table, and presumably she wanted to read it.
I can't believe SC sat still for all that either, it has so much less probability than her doing it herself. To take that further, right-handed people tend to shoot themselves on the right hand side of their body, left-handed on the left - SC's wounds are to the right side of her throat: another small detail a murderer wouldn't have thought if. And female suicides tend more to shooting in the neck rather than the mouth or temple, which both disfigure the face.