40 lbs is a good weight for a kid. Make sure he can handle it good in the field. I go with a good carbon arrow and a cut on impact broadhead. I hunted once with a lady with a will tuned 35 LB short drawed compound bow with a carbon arrow and a cut on impact broadhead. She got a pass through on a nice 8 point buck quartering away from her and the arrow skidded up the lane the buck was standing on after it passed through. She thought she had missed it at first because she seen the arrow skidding up the lane, but than the buck drop dead in sight of her at about 40 yards.