Bedding
How tightly the rifle's action sits inside the stock or chassis. Glass bedding, pillar bedding, and chassis systems all aim for zero movement under recoil.
A loose action in a stock will shift point of impact between shots and between range trips. Bedding eliminates that play and locks the action in one repeatable position. Glass bedding pours epoxy around the action to take a perfect impression. Pillar bedding adds aluminum or steel sleeves around the action screws so screw torque doesn’t compress wood or plastic.
Chassis systems sidestep the question entirely, since the action drops into a machined aluminum cradle with no flex.