243 or 30-30

I agree on the fit suggestions and the .243 would be hard to beat and can easily be restocked as they grow. I don't recall what you game you plan to hunt and that is another nice advantage of the .243 going from light loads for varmint and 105gr for deer sized game. A wide variety of ammo is available.

For an AR platform in 6.8 would be good as well with collapsible stocks for fit and there would be a serious "cool" factor most kids would love.

All the above options could be used their entire hunting lives.

Yes, the adjustable stock on an AR offers the greatest range in length of pull, as well as high-capacity magazines that make for better practice sessions.

I haven't checked the numbers but suspect a reduced recoil round in 30-30 or .243 would be about the same as a standard .223.

If a fellow is a reloader or has a buddy that is, the 260 or 6.5 CM with a 100 gr bullet has very little kick. Load it down a bit and the recoil will even be lower. During deer season I use the 120 gr Nosler BTs, and after the season I coyote and pig hunt with the 100 gr BTs. The kids and small ladies have zero problem with the recoil when using the lighter bullets. It’s about the same as a 100 gr bullet in the 243, and when the kid is bigger you’ll have more gun than the 243.

300 black out. 110 gr Barnes tac-TX

-haha- So true...

Ok I’ve shot every caliber out there and killed deer with a lot of them. The 243 years ago was the ideal caliber for kids but in the last 15 years that has changed. I firmly believe that the 260 Rem or 6.5 Creedmoor is hands down the best caliber for kids and even adults. With today’s bullets it meets all the requirements for varmits, deer and even elk. We have 8 rifles in the 6.5 twins. We all shoot 120 Barnes tsx, lrx and the Hornady 143 eld bullets. You can reload or buy great manufactured ammo from Barnes or Hornady in these bullets. They are very accurate and take broad side shots on deer easily or the Barnes bullets can pass through from butt to chest. Elk are easily taken at 300 yards plus every year with these bullet combos. With all this said you can barely notice any difference in the kick between the 6.5 twins or a 243. For the last 7 years my family have taken 30 plus deer with them most fall in their tracks, the ones that do leave the scene have a hole bigger than a golf ball on the exit and blood trails are easily trailed and animal recovered. If you want some more technical reads and actual field data I can send you a link to the reads if you pm me your email. Also the 6.5 Swede would fall into the same category as these two calibers if you come across one of them. Oh and if you reload the accuracy of these calibers is insane. I have a lot of 1/2 moa rifles some costing a lot. But I found that the Remington 260 rem in their vtr rifle is an awesome little rifle. So much so that my son uses one and I have one I hunt with and I though so much of the little rifle I put a Nightforce Beast on it and have taken deer out to 450 yards with it on several trophy hunts. People laugh at the setup but after they see the results and handle the rifle the agree with me also. My second favorite rifle is the 6.5 Creedmoor in Bergara’s Premier Approach. Very smooth with a medium weight barrel and shoots Barnes factory 127 LRX less than 1/2 moa at 200 yards. So I know this is a lot and just wanted you to know that there is a caliber that will handle pretty much anything they want to hunt.