It has been my unfortunate experience to have to endure the long and hard road of finding scope failures on 2 different rifles at the same time of late.
I am not going to disclose the manufacturers involved, nor the cost of either one, other than to say one can be sent in for repair by anyone with no questions asked and the other requires the original receipt and warranty card. I only mention this to establish that names and cost do not seem to matter when it comes to scope failures. They can and will be costly in terms of wasted components and time, not to mention a few more gray hairs.
In short, what I mean to convey is if your rifle seems to have a propensity to shoot 3" groups when it feels like it and 1" groups on other days, It JUST MIGHT not be the jerk behind the trigger causing all the trouble. Consider swapping out the scope before you waste 6 months and untold $$$ in primers, powder and projectiles before you question your optics.
Those utilizing iron sights can now smile smugly and browse another thread. I can only envy such eyesight.
Just a reminder, all is not always what it seems.