I bought a bunch of cheap guns off a guy and in the bunch was a Belgian Flobert "parlor" rifle. Extractor is stamped "28". The bore mics .284-.286" (depending on where calipers land). SO, I assume this is some sort of 7mm rimfire. I have never seen a Flobert that was NOT rimfire. Granted, I don't know a whole lot about them but has anyone heard of such a cartridge?