I have an 18" 243 and I've used the light Nosler BTs to great success. I toyed with the Barnes, both 80 TTSX and the 85 TSX, and never fell in love. But I also hunt Texas whitetails who are about large dog sized.
Agree that it's a great youth rifle. Almost zero recoil and the BT is nasty. If you want to go above 3000 fps in a barrel that short, you really do have to run the lighter bullets. Nosler says the BT expands down to 1800 fps (I think), But you really want to have some room for error and be above 2000 minimum at impact. My 90 BT load is at 2970 fps and it's not really being pushed. Just happened to find an accurate node. I'm 2000+ out to 400 yards. I wouldn't go hunt an elk or muley with it at extended ranges, but it does fine for my work.