You are ignoring th ebullet that grazed Nevill was found int he master bedroom.
In the meantime you have zero evidence any casings were moved to the master bedroom and there is no motive for police to do so.
In my presentation Ralph was never in the bedroom to be grazed by any shot, as you put it. Ralph was undoubtedly shot at least once somewhere near the top of the main stairs, perhaps twice, (wounds 8 and 7). In my opinion he was never inside the main bedroom at all. He made it to the kitchen, managed to make his distress call to Jeremy, followed by his distress call to the police, informing them that his daughter has got one of his guns, and is going berserk. It seems obvious to me that once Sheila shot Ralph on the stairs (wound 7), that the bolt action load mechanism jammed forcing Sheila to return to her bedroom to collect the preloaded anshuzt rifle filled with 10 cartridges, with another 5 live rounds on standby on top of her coded handwritten note on her bedside cabinet. Once in possession of the loaded anshuzt rifle she set off down stairs to finish off Ralph. In the meantime, Ralph had made his calls to Jeremy and the police (3.26am), and was either still in the process of talking to police, or had just finished, when Sheila turned up in the main kitchen with the fully loaded anshuzt rifle. As she entered the kitchen, Ralph half turned his body and his head, and at that precise moment Sheila fired two .22 subsonic bullets into his mouth region...