The US Olympic Team has learned that some lots of Eley Match (black box) shoots as accurate as Eley Tenex.
I think you need to shoot 20-shot groups with rimfire ammo testing for accuracy. With all the variables in ammo as well as having to hold the rifle still near 3 times as long as a high power rifle after the firing pin smacks the case, few-shot groups don't tell much with .22 long rifle ammo.
The amount of torque on the stock screws also makes a difference. Try different amount of inch-pounds of torque and see what happens. Most bolt action rifles seem to do best with between 20 and 30 inch pounds of torque. And the barrel has to be totally free floating.
US Navy Distinguished Marksman Badge 153
Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master