Daryl, that's about what I had in my head. I was too distracted (read: lazy) to investigate all of the dimensions but I assumed the bulk of the chamber was sized for the original 8x50R in order to use the original en bloc clips and bolt head with whatever 22 caliber cartridge was intended. As Lancaster points out, the .220 groove does lead to the rimfire. That would require a different firing pin or offset chamber. Either way, it's an odd pairing what with the rest of the rifle.