I've read conflicting descriptions of how .22LR cartridges are primed. One source says the primer is a mixture poured [?] into the case, which then hardens, and the powder is added. Another source says the primer is in the form of a thread laid around the base of the case and powder added.
In any event, someone out there seems to think that Lugers will fire .22LR with stock firing pin/breechblocks. There have been two barreled receivers offered for sale. Neither uses the Erma sub-caliber 'kit'. I've never seen a fired .22 case with a center strike, but the bit bucket at the club has about a dozen .22 rim mis-fires on any given day.
I shall see.