I always suggest to someone complaining about their rifle's accuracy to get someone else behind thee rifle, someone who is a known good shooter.
Normally two things happen - they either ask who to get, or the conversation ends and they walk away mumbling about how it is not them!! LOL
I have often got someone else to shoot my rifles if they are scoped to verify, but in the case of 90% of my long range rifles, if I have doubts about the accuracy, I take the irons and sling off , and put my 9-36X IOR on and bench the rifle at 500 meters and 1,000 meters - that normally ends up with me mumbling that my form needs some rework , but happy that my load and rifle are still fine!!
Cat