I want to get something for my 9yo son, and I like the idea of a 20 gauge/.243 or something like that. Not dead set on caliber. Over/under would be nice but I would be fine with a quick barrel swap set up as well. I dont know where to look online, searches for combination guns have not been all that productive. I think I heard of one that has 20 or 12/.243/.22lr but its a barrel swap for each 3.