My 9 year old grandson killed 2 deer last year with a standard 357 and handloads. He shot a 243 with reduced loads and stood up to it, but you could tell it bothered him. When he shot the 357 there was a slow grin that just consumed his face. He therefore practiced quite a bit. ( I had to run an ammo budget deficit) When the time came, he very calmly put one through both lungs of a doe at about 70 yards, she jumped and ran about 30 yards and turned and looked back, I had him put another through from the other side, she fell right there. The second, he waited until the single spike was about 60 yards and starting to move into cover and made a head shot right behind the ear. He is permanently hooked now. If I had used a heavier rifle, I dont know if it would have turned out as well. If your child is only 7, unless he is a giant for his age, I would err on the side of caution. You can always get another barrel later.