I took a ride down to my LGS and he agrees: .22LR chambers will fit a Stinger. That's cool, because I have a .22LR chambering reamer coming.
I also bought a box of .22LR 'Aguila' Super Extra [with label on box 'Eley Prime', whatever that means], 50 rd box @ $5.00. He had one brick of that come in from distributor, and a brick of .22 Subsonic ammunition, that looked like a .22 short with a real long bullet. I didn't think that would work any .22 action I have, so I left that alone. (I don't have any bolt action .22's or revolvers).
I was thinking that the Erma barrel inserts are longer than the Luger barrels because it would take longer to build up the pressure to toggle the action than if they made it the same length as the Luger barrel...
Dave - Does your Erma toggle have a model number on it??? This one says 'SE 08/2'...
Edit: I went back and bought a box of the 'Sniper Subsonic' .22's...Looks like a .22 short to me!!!
(And in the 15 minutes I was gone, someone came in and bought the rest of the .22LR brick)...