Well like mentioned H4895 has worked good for me and my three grandsons. My .308 is a Ruger Compact and only has an 16.5" barrel on it. I'm not setting any speed records with it even using top end loads.The oldest now 15 started out using those loads when he was not much past his 3rd birthday. I used the lowest charge weight I could with the Nosler 125gr BT bullet and they shot really well out to 100yds. That said however I only let him use them out to 50yds max.
He started shooting them around the first or middle of March that year, and shot his first hog with them two weeks before his 4th birthday around the second week of Nov. After he got a bit more experience I upped the load and also moved up to the 130gr TTSX. He liked that one a LOT, and shot a bunch of hogs with it as the years have passed by. As he got a bit older and more accustomed to the recoil we just moved the charge weight up a half or grain at a time. He hasn't let up since. Also those 130gr Speer bullets shot very well. I used a LOT of those for practice as they were a fair bit cheaper than the Barnes.
While NOT trying to change the subject but simply to add to the loads with H4895. With the two younger ones, I used the Nosler 100gr Solid Base bullets loaded the same way only in .243. They have both had success with those as well.
Whats great about the loads using H4895 is that you can start out so low and can then work up all the way through the full spectrum to the top end load for that bullet weight, and there are usually a couple of accuracy nodes that simply drill the bull time and time again. That and you can use the data for ANY bullet weight which has H4895 data listed.
Having the three grandsons, at 9, 11, and 15, I fully understand your quest and wish you all the best on it.