The Pope barrels had the bore centered at the muzzle and off-set at the breech end. The bore is straight, not curved. The bore is simply not concentric with the exterior of barrel.

A fancy piece of machine work!

I believe the boring and rifling was done with everything concentric.

Then, the barrel blank's exterior was machined on a lathe with the bore-end centered and the breech-end held off-set. This resulted in a finished barrel with the bore slightly angling from the breech, but, appearing centered at the muzzle.

A number of German makers (Mauser, Walther, and others) and European makers produced such barrels for Sporting and Training .22  cal. rifles in the pre and post WW2 era.