Yes I was asking this question because I was wondering if it would have been possible for Bamber to carry out these killings without anyone noticing things such as gunshots, screams and someone arriving at the farm.
The distance to the nearest cottage is in the region of about 100 metres as the crow flies. The bedrooms and kitchen where the shooting took place have windows located on either the South or West sides of the farmhouse (in other words facing away from the cottages), and the only crime scene photo available which shows an open sash is one of the parents' bedroom window on the South side, although this could have been opened by the police after they entered the property. An Anschütz 525 is not all that loud close up, even without a moderator fitted. So the sound of rifle fire through an open window reaching so far is really a non-starter. The same would go for any screams that may have occurred. The surrounding trees in full leaf would have added to the sound deadening effect.
I don't know how familiar you are with the case, but there is an ITV documentary of arms expert Philip Boyce firing a similar rifle, although the one he used was a carbine version and not the long-barrelled type like the actual murder weapon (15:30 onwards)...,
http://www.youtube.com/watch?v=_i2CjYDJGTo