Some wisdom would be reading comprehension.
I never said .410 and 22LR could not kill. I said 20g is superior to either of them . Which it is. In particular the 410.
I do realize that this is off-topic but I just had to comment.
20GA, no doubt, has superior
killing power to a .410. If that is what you are saying, then you are correct. However, for small game (and assuming the point of hunting small game is to eat the small game) the .410 has the distinct advantage of not turning your game into pink mist. Depending on range, choke, and shot size a 20GA tends towards blowing the entire front section of a rabbit into pink mist and "hamburger". This is much less likely to happen with a .410 and with good skills the .410 is just as likely to kill the rabbit. So, what's the advantage of the 20GA? Range? Well, that's where the .22 comes in.
Back on topic; the Model 42 in .410/.22LR is a very interesting gun. I think it would be an ideal grouse/rabbit gun. I've hunted grouse and rabbit enough now that there are basically two types of opportunities to shoot these two species; 1) at a distance when they hold still, thinking you don't see them, and 2) when they are right under your feet before you know it and they flush or bolt. The .22 covers #1 and the .410 covers #2. I can't think of a better combination for this unless one does not plan on eating their prey but instead simply wants it vaporized. Then perhaps a 20GA + 30/30 would be better.
Having said all this, the Model 42 is a wopping $469 at Cabelas. One has to consider the alternative option of slinging a lightweight, scoped .22 on their shoulder, for the long shots (everyone already has one, right?) and carrying a $179 H&R Pardner .410 in their hands for the quick, running/flushing shots.