Sheila could have been sitting,propped up against the bedside cabinet and after the first shot it would have jolted her,with the second shot following in quick succession just by a mere touch of the trigger as because it was a comparatively new rifle and a semi-automatic one it would have sent her in the position that she'd been found.
The above " could " have happened,although I don't believe it went that way. I have my own thoughts,especially as the rifle had been just placed on Sheila's body because it wouldn't have landed like it had if she'd just shot herself.
I've always wanted to know how DCI " Taff " Jones came to the conclusion that it was a murder/suicide. Just because a weapon appears on a body doesn't always mean that that person had been responsible.
I'll have to re-read about which bullet wounds were contact shots on both June and Neville.