Whether a rimfire is safe to dryfire or not depends on the design of the firing mechanism.
When in doubt, I use a fired empty case to absorb the firing pin impact.* Rimfire or centerfire.
If a rimfire design allows over-travel of the firing pin, protrusion past the face of the bolt, the firing pin will impact the edge of the chamber if there is no cartridge in the chamber.
If a design stops the firing pin before it impacts the edge of the chamber, it is safe to dry fire. Many target guns are deliberately designed to be safe to dry fire for trigger pull/sight alignment practice.
I have checked several of my .22 bolts to see how far the firing pin is allowed to go.
Many (not all) are designed to prevent the firing pin from protruding from the bolt more than the thickness of a rimfire cartridge rim.
Some of the older single shot bolt actions are really bad about having excess protrusion, but operating a single shot bolt action means you are usually aware of whether there is a round in the chamber or not.
wisecoaster post #12 My beginning pistol course instructor wanted me to dry-fire it, and said it was OK because it's a center-fire pistol. I advised him that the [Beretta 92-FS] owner's manual specifically advised to NOT dry-fire it.
I have a centerfire CZ52 pistol and the manual advises against dryfiring it. If the firing pin is not cushioned by striking a primer the shock can be too much for the cast steel firing pin. The Czech Army field repair kits for the CZ52 are mostly spare firing pins and the spring clips that retain the grip stock halves.
Ruger usually has good ideas. Marketing the SR22 pistol (no hyphen) and the totally different SR-22 rifle (hyphen) is just confusing to me and not a well thought idea. CZ (factory) made vz52 (Model 1952) pistols and rifles. The rifles were imported first and sold in the US as "vz52". When the pistols were imported later, they were sold in the US as CZ52 to distinguish them from the rifle.
______________________________
* There are rimfire snap caps to absorb the firing pin impact. BLACKHAWKNJ post #5 recommended bright yellow 4-6-8 drywall anchors for dry firing. They have the advantage of being clean, not leaving old primer and powder residue in the barrel like spendt casings do, and are almost as economical as spendt casings. Plus CMP safety flags are bright yellow.