The .224 64 grain Winchester PSP will do a job on any deer sized critters.
Hard to find, and doubt they are made anymore, but I do have a bunch of them that I used in a 223 TC contender pistol on deer......
I shot two does with a Bushmaster at 270 yards with a 53g triple shock, both ran, no blood, lung shots = running deer and we found both of them about 75 yards away. We shot that rifle a lot on the range at 250 yards and the Leupold 6.5x20 with target knobs is the key along with the JP trigger. I would not shoot another barnes in this gun. 60g partition rules the day, 64g Nosler bonded, 64g Winchester, then get the 55g Hornady. Never tried the 65g Sierra.
I can not stress how good the 60 partition is on deer, and in a 22/250 the 60g partition is a as good as a 30/06. The Remington 700 with a 14 twist will barely stabilize the 60 partition with 1 1/2" groups, but the 12 twist is the twist for this bullet.
With the light calibers and good tough bullets, shoot through the shoulders, take their running gear out from under them. Neck shots can be sucker shots from a distance. I am not a believer in Tripple shocks unless you have major horse power behind them.
Hog shoot'en, well they are pests. With a 223, you are pretty much counting on hitting the central nervous system on a DRT kill. So, a quality AR, good high power glass, where is the challenge? Shoot them in the head/neck and lung shots will = running hogs same with deer.
Last antelope I killed was with a 223, 55g Win soft point at 3100 MV, he was 470 yards, and dropped like a toilet seat.
Give a kid an AR, target rich environment, he is going to gimp up some hogs, good reason to get him to the range and keep him shooting. Dead hog is a good hog.
I don't know how large your grandson is, but an AR is an unwieldy rifle to handle for a young child. We started our nephews off with TC Carbines in 30/30 with low recoil Rem ammo, they were awesome on killing deer out to 150 yards, they also wanted to shoot blue jays, hawks, chip munks, squirrels, about everything that walked, flew, or crawled. We had to sit in the stand with them and train them that they were not going to attack us plus the right and wrong of gun handling. My little nephew at 7 years old sat in my lap and killed 5 deer in one season, a bob cat, and two crows with that TC in 30/30 with a 2x-8x leupold on it. The TC is a very handy little rifle, not heavy or cumbersome for a child, and I cut the stock for a perfect length of pull for him so scope acquisition was perfect for his size.
With your quality AR, I hope you get to the rifle range as much as you can, grand sons love to be with their grand pa, really no matter what you are doing as long as you are doing it together. I used the "mini" clay pigeons for my nephew to shoot at, and they measure 2 3/4" in dia. If you can work him up to shooting these at 200 yrds, then get him to shoot the pieces that are left over, he will have all the confidence in the world with that rifle. Aim small, miss small...preach this to him.
As soon as your grandson can handle a 243 with a cut off stock, then the 80g tipped triple shock is a Mack Daddy round for big game along with the 95g partition..savage Axis is a good place to start. Also, the 22/250 Savage Axis with a 60 partition would be excellent.