When I fit an action I would shim it to be touching in the stock just infront and behind the fixing screw and no where else. especially along the length of the air tube. if the tube touches at the front and the action at the back the bolt so many rifles have going up through the stock into the action can bow the action as it tightens. This can often be seen by the gap between the end of the barrel and air res closing slightly as the screw is tightened, I have seen this many times even without the bolt feeling tight. Actions with a front barrel support will still shift zero if bowed in the stock. This bowing will vary as the wood expands and contracts. Shim it so you can slip a sheet of paper between the air tube and stock along its whole length when the stock is tight and you will eliminate the woods influence on the action.
HFT, for people with only 2 buttucks!
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