I don't think the silencer was used: I think it's completely fabricated evidence. The only person who says the gun was fitted with sights and a silencer before the killings was a gun dealer who illegally kept his own identical gun off the premises, and returned his own identical silencer at the same time he brought his gun back, and stood to gain from Bamber's imprisonment.
If you look at the photo of the gun balanced against the wall next to the 'gun cupboard (a posh title for what in reality is just the space under a small tight staircase) without the moderator and compare it to the photo of the policeman holding it with the moderator, I don't think it would even have fitted under the stairs with the moderator on.
JB had used the gun a lot and he had been on shoots with shotguns and objected to anything other than vermin being killed: he would have known how long and unwieldy the gun was with the moderator - it would have been extremely impractical for moving from room to room and I'm surprised there wasn't paint damage to door jams etc. He would also have known it is not a silencer and scarcely deadens the sound of the shots. He would also have known that animals like foxes are still able to run off after being shot once with a .22 - it would be plain as a pike staff you'd need more than that to take down Nevill.
That's a double-barreled shotgun balanced against the Office/Den wall, not the actual murder weapon - an Anschutz 525...
http://miscarriageofjustice.co/index.php?topic=633.msg71558#msg71558Anthony Pargeter discovered the Bambers' newish Anschutz complete with moderator and telescopic sights alongside his own weapon in the gun cupboard, and I've no cause to disbelieve him. His was lying on the floor cased, and theirs propped with the butt on the floor, uncased next to it.
As it was referred to as a "gun cupboard" then it obviously was used to store weapons at some stage or other, and imo could easily contain a fully fitted-out Anschutz because the winders and additional normal treads of the stair continue to right as in the photo below and as drawn in the GF plan (S3)...
http://miscarriageofjustice.co/index.php?topic=633.msg25947#msg25947An Anschutz 525 is not unwieldy even with a moderator. I've used a quality air rifle of similar length and weight to an Anschutz and that was easy to control, even more so when held with the butt under the armpit (as seen in Wild-West movies) to shorten it. The noise in a confined bedroom space indoors with sound bouncing off hard surfaces such as walls, ceiling, doors, and cupboards would be louder than if the rifle was fired outdoors too... hence his reason to use a moderator to reduce it.