Try playing with the torque on your lug bolt, go mildly firm and shoot a few shots, then try good solidly firm, if you see a difference try it even firmer and see if there's a torque it likes. I've had a few rifles that weren't shooting worth crap that were very fussy about action torque and improved dramatically.
I have the heavier model 70 coyote, it shoots the 55's under half an inch but won't shoot the 95's under an inch and a half or two inches.
Also try resting your fingertips on the barrel out toward the end of the stock, or if you have enough scope clearance rest your fingers across the barrel. I've seen tighter groups by changing the barrel resonance with some dampening on the barrel.
Some rifles just won't shoot, it happens. If mine had shot the 95's great and the 55's lousy I'd already have a new rifle, I wanted fast and flat out to 500 yards and I've got what I want. It puts coyotes down with severe prejudice.