Just in case someone does not know, although I think that they had only one shotgun barrel, the gun that was know as the "Drilling" (which I believe was a brand name, but were other makers), and variations including a German WWII survival gun that was issued to some German bomber crews, had multiple barrels including a shotgun, large center fire rifle, small center fire rifle, and .22 rim fire. There were civilian rifles in Europe for sporting purposes also, that were intended to shoot game of opportunity, be it hare, boar, game bird, or stag.
Whoops! Now that I have thought about it, they were more likely to have two 12 gauge shotgun barrels, one large center fire rifle, and one small rifle (either center fire or rim fire...I cannot remember for sure; been too many years).
http://en.wikipedia.org/wiki/Combination_gun