Aren't you now being subjective? Bamber WANTED (edited from original post) the crime to look disorganised and as though Sheila were responsible. Execution style head shots would have raised questions.
There's a crucial difference between JB v SC:
If JB was responsible he had 3 adults to murder one of which needed to look like a suicide. And according to the prosecution the adult victims were spread over 2 rooms.
If SC was responsible she had 2 adults to murder and could take her own life as and when it suited. And according to the prosecution the adult victims were in 1 room.
If SC was responsible her task was arguably much easier.
If JB was responsible,a marksman at Greshams, he had to make the scene look amateurish and manic; a fine balancing act between this and maintaining control. He could not run the risk of being over powered by the adults. Or one of the adults arming themselves with one of the other firearms. Or raising the alarm from within. Or fleeing WHF to raise the alarm.
The prosecution case is that JB entered WHF under stealth and opened fire on his parents in their bedroom. This being the case he would have taken them out in the bedroom. A few crazy shots and then moved in for the kill with shots to the head. This would look amateurish by way of random shots hitting and injuring and then going for the head when the victims were subdued. This would be over in seconds then swiftly across the landing into SC's bedroom killing her in her own bed.