Virtually all modern .22 rimfire firearms have counterbored chambers and limits on firing pin movement. Basically, the pin stops before it can bottom out in the counterbore and contact the chamber.
Older guns often didn't have couterbore or pin limits, so the pin could hit the edge of the chamber.
I have a number of .22 rifle, revolvers, and autos that have been dry fired 10's of thousands of time with no problem.
If it makes you feel better about it, put fired cases in the chamber, it can't hurt.
The one modern rim fire I won't dry fire is the Colt Trooper Mark 3.
Some of them have firing pins that are too hard and can break. The Mark 3 must be returned to the factory for replacement.
If your manual says don't dry fire a gun....don't.