Actually, the 45 Colt round would sink into the .45-70 chamber past the rim. I've tried it in a BFR. (No, I didn't try to fire it that way.)
I'd kinda like to shoot this one.... Once..... 
Its two barrels. One for the colt/.410 one for the .45-70. they also have a two shot .45-70 model. Somehow, I doubt they let you test fire it before you buy.

I mean, my Bond in .357 was surprisingly manageable. I never shot more than a few in a row, but no muzzle control problems or flinching or anything. You just wouldn't want to run through a box or anything, and damn it was loud! It was actually pleasant with .38. This seems a tad more extreme.

FQ13