I agree, although I'd rather have .30-30 or .308, being on this side of the pond. Or .44Mag, because it gives up some range but is a lot smaller per round.

The problem that rears it's ugly, ugly head everytime I mention this is sights. .22LR has a certain ballistic profile. The bigger rounds have another ballistic profile. Get one sighting system that can handle both. The best way would be to put optics on it, with a see through base and iron sights. So which one do you put the glass to? The other way would be to determine hold X-high/low at Y-range for one barrel and zero for the other.

It is a great idea, but I'm just not sure it can be made viable. Trust me, I've been trying to work that part out for a long time.