I was trying to work out which bullets came from which magazine. There's no reason why there should ever have been ten bullets in the magazine. I think that one magazine-full accounted for four shots to Nevill in the bedroom, and maybe five shots to June. Then the killer ran out of bullets.
Another magazine accounted for the shots to the twins.
The third magazine could account for four shots to Nevill in the kitchen, two more to June in the bedroom, and two to Sheila.
This issue of the wandering cartridge does change things a bit, but I'll have to think about that one.