There precious little lost when shooting a modern slug from a 20 ga.. The problem with porting is that it doesn't adequately address the rearward motion. The barrel is much too thin to provide much direction to the gasses and a shotshell produces little gas.. Adding weight will make the gun harder for a kid to handle, sorta defeating the purpose.. If leagal in you state a rifle may be a better idea.. Single shots such as the NEF guns and many others (mostly imported) are available and the calibers such as a 223 or 243 would be great for a youngster.. 45-70.gov--- I too hate brakes but have used them when needed.. With ear and eye protection (only the best...) they can be safely used.. I hesitate to reccomend one for a child as I've read that the deleterious effect on kids is worse than adults.. I started my kids off with sound silencers, mini sonic valves when hunting and at the range. they no long use the ear protection but shot well. They started with a 243 winchester amd 100 grain Nosler partitions.. worked quite well thanks.. The Daughter took a 130 inch class buck her second season and many other deer since.. Last sunday nite she walked the 'White Coat' ceremony at the vet school here in Missouri,, a couple more years and she'll be through.. Sorry but I just had to brag a bit!!!