meketrefe
.450/400 Nitro Ex
I understand it is marginal but in the woods at close range modern high performance loads are still pretty decent in terms of wounding potential and given one chioces game on the light side and in close range so the kid can have a good experience.Actually the reason a .410 isn't legal for big game dates back to the shot gun only time, a .410 is a caliber and not a "gauge" thus it's not a shotgun. Or it could be that it's not considered powerful enough, Or so I'm told. I'm also told that they are very accurate with slugs but have no experience with a .410 other than shooting clay birds with my TC Contender.
The thing is that good hot loads for modern firearms are scarce and that is why they might exclude them. It is like the grizzly 357 loads, not all firearms can take the heat so they come with a warning.
Personally I would wait a couple of years and introduce the kid to a moderate yet decent deer killer like a 30-30 or a mild 120gr 7-08 or 308.
They sell the youth rifles in those with the blocks for the stock that one can add as the kids grow and keep the gun for ever as they take aftermarket stocks like a nice savage axis or savage 10. Those make great youth guns that one can grow woth amd keep.