Well, since you now apparently now have two .22 Mag rifles misfiring with the same ammo?
http://www.thehighroad.org/showthread.php?t=642703
I'd have to say you got your ammo contaminated with oil, solvent, or moisture somehow.
I have been shooting Winchester & CCI .22 Magnum ammo for the last 40 years, and I cannot recall ever having a misfire.
If there is a more reliable Rim-Fire round, I haven't seen it yet.
The only other possibility I can think of is, the chambers are badly fouled in both rifles, and the cartridges are not seating fully when you close the bolt, or in this case, bolts. Seating them with the firing pins takes energy they can't spare and still fire the primer mix.
Clean the snot out of both rifles with a bore brush & solvent.
Also, clean the bolt faces and barrel / breech faces, including the extractor notches.
Also, see if there are dents in the barrel breach-face's where the firings pins have hit them from dry-firing.
If there are, the dents are not allowing the FP's to crush the cartridge rim against the barrel like it should.
If that doesn't help, buy some fresh ammo and try that.
rc