I don't really understand why many who believe JB guilty are keen to preserve the idea NB was shot in the bedroom. As puglove has pointed out even if NB was shot on the stairs it wouldn't make JB innocent. At best all it can do is lend support to NB phoning JB.
I've just copied Hartley's reconstruction from Blue:
The killer enters the bedroom, stands at the foot of the bed and starts shooting, shell casings are ejected to the right.
June is shot a number of times, she sits forward and collapses out of bed on her side.
Neville is shot a number of times but manages to run past the killer out of the room and down the stairs. The killer pursues and after a struggle in the kitchen Neville receives the 4 fatal shots.
The killer returns to the bedroom where June has managed to move around a little and shoots her an additional two times whilst standing in the doorway, the cases eject to the right.
The ballistics evidence show NB's lip and jaw gsw's were inflicted when the barrel was inches from NB's skin. To err on the side of caution I will go for 11 inches. NB was 6'4" tall. A standard bed is 6'3" in length and a King and Queen 6'6" so I'll assme the later. That's 78". The length of the rifle is 43".
Length of bed = 78"
Length of rifle = 43"
Distance of shot = 11" approx max
Deduct the length of rifle and distance of shot from the length of the bed leaves 25" meaning the perp would need to hang over the end of the bed to inflict the gsw's to NB's face and lip. How would NB then get out of bed and get past the perp to sustain the gsw's to the rear of his shoulder and elbow/chest.
Holly, just because the bed is 78" long doesn't mean that Nevill was lying flat with his head jammed up against the headboard... Geez!!! He was probably leaning forward about to get out of bed because he was aware that he was going to be shot. The rifle could have been held, not in the conventional way with butt end up against the assailant's shoulder, but with its body thrust forward and muzzle close to Nevill's face. No need therefore for any 11" gap. It's so easy to imagine, I can't understand why you don't see that. You're too reliant on perfect precision and measurements which are way off the mark.
There was no blood on the bedding maybe because, unlike June, he was only shot twice and was quicker to get up and out of the room. But even if there was the odd spot or two, either forensics missed it or the police burned the relevant sheet(s) with the stains.
As for the two shoulder and arm wounds, if you insist that they occurred with the perp standing in the doorway, or on the landing, or on the winders, while Nevill was going downstairs, then you could easily substitute JB for SC with the same result.