Originally Posted by scsims
I've noticed that one of my rifles the crosshairs jump a little when dry firing. Any ideas on how to reduce it?
Every fixed power scope I've ever used does that on all my rifles; rimfire and centerfire. Their windage and elevation adjustments are spring loaded pressing the erector tube in the scope hard against the flat of the adjustment screw. It's totally normal that that tube will vibrate a tiny bit and you see that when dry firing.
In most variable power scopes, the two lens groups that slide back and forth when changing power will shift position a tiny bit when dry firing the rifle and that also makes the reticule jump a bit when the rifle's fired; dry or with live ammo. Their fit is not zero tolerance in the tube they slide back and forth in as the power is changed. They also can change position as the power's changed; the reticule moves in an irregular pattern about the collimator. Sometimes as much as 1 MOA. Which is why many folks wanting best accuracy with variable scopes set the power to one limit and keep it there; the scope's more repeatable that way.
As long as the reticule goes back to the same position after jumping from mechanical shock, there's no problem. Put an optical collimator in the muzzle, zero the scope on it then dry fire watching the scope reticule on the collimator's reticule. If it goes back perfectly each time, no worries.
And no rifle action I've used has its bolt jump when firing live ammo. The firing pin tip does not dimple primers enough to let the cocking piece strike the bolt camming surface to push the firing pin back. But when dry firing without a round in the chamber, it's as common as sunrise every morning. If this happens with live ammo, then something needs fixed; probably the cocking piece on the firing pin needs its cam point ground back a few thousandths.