Vol 423,
fuhrmann and bavarianbrit are correct, an Einschublauf is either soldered or glued (epoxy) into the barrel which has been reamed to remove the rifling and the taper from the chamber to fit the liner. The 5.6X 50 R is a popular cartridge for hunting Roe (Reh)deer and was introduced in 1969, by DWM, at the request of F.W.Heym because they were having trouble with extraction of 222 Remington Mag (rimless) in their Mod 22S o/u Combination guns. Where legal, as in Alabama, the 5.6 will take whitetail with a careful shot placement, especially when handloaded with a 60 grain Nosler Partition bullet.
Mike