Bench Testing My Air Rifle.....

For the past few weeks my air rifle has been dropping quite a few shots, to eliminate the rifle being at fault I stripped the rifle down and bolted it into a weighted down workmate to bench test it and different pellets.
BMJnr helped me down the club and we shot 12 diagrams and this was the best group of five pellets so I have now eliminated the rifle as to be at fault, only things left is the scope and Me.
My shooting average for Rim fire bench rest is 299.4 out of 300 so I think that eliminated Me (Hopefully) so that leaves the scope, and I have always thought that this was Parallaxing very badly from the day I bought it, so I must now change the scope for a known good one off another rifle.