A very nice looking gun, Daytime Dave. If you were to shoot it more, it would be neat to hear your thots on it. BTW, how would you "name" such a configuration when it is a breakaway o/u in two calibers? Maybe they chose the first numeric digit from each caliber to call it a "42."
I agree, JEBAR -- it is some kind of rig. I've seen the Savage before. But the one I found made by Chiappa Firearms really was a surprise to me. I think Chiappa has the rep of going more for "extremes" in firearms configuration. I know their revolvers are most unusual after reading about the Rhino model.
But back to this rifle/shotgun config. Take a peek at this
Chiappa X-Caliber http://chiappafirearms.com/product/2696
Almost hard to believe the write up. They say the original config was
"a rifled .22 LR and a smooth bore .12 GA -; this rifle can fire up to 12 different calibers thanks to the 8 steel adapters supplied." I'd say there would be a challenge keeping that variety of ammo in stock! But it would be fun to see one of these --- actually, double fun would be to try one out!