I've introduced several thousand young people to firearms.
Specifically, because he is a male, his physical changes in the next 5 years make choosing a gun for today a point to consider.
If you wish to keep changing guns as he develops, then at our club we would start him on a single barrel 20 w/ sub sonic rounds if he was smaller. When he could dependably hit low 7 and unload/reload the firearm without interference from his "coach", we'd add complexity by moving him to a pump 20, but single cartridge at a time. If he is able to comfortably operate the 5 lb pumps, depending on physical strength, we may/may not move him up to one of the club Beretta 20's. Heck, some boys go from 70lb noodles to little linebackers in 6 months.
Our keys being, size and strength, safety awareness and mechanical aptitude in handling, and success on hitting simple targets. You need all three legs of the stool before we move a youngster into more than one cartridge.
The Remmy 1100 20's weigh far too much for 90% of our young shooters. We've had dozens fail to operate right out of the box (they are a common youth raffle gun) at the club. It's an immense disappointment to the lucky kid that won one, when it won't work, and has to be sent to a service center before they even get to use it.
Because deer hunting is really why most of our youth are at their hunter safety training, the Mossberg 500 youth 20 has become a popular (and liquid) firearm, because they come with a coupon for an adult stock, they can have deer sights added easily, and they have a youth stock that is shaped for a youth, not an adult that is short. They are very accurate with slugs, and are steel ready for introduction to waterfowling.
Whatever you do, it has to be fun, and safe.
We had a tragedy just a couple years ago here in MI.
