My kids shoot a cut down T/C Black Diamond. For the past two years, we used 75 grains of 777 under a 300 grain XTP. This year I had a large box of 240 grain XTPs I picked up on sale after last season and that is what they use. They have killed two or three a year with this combo, including two so far this year. An excellent combo. My kids are 9 and 11 and shoot it well. My general rule is only broadside shots to the heart/lung. Of the 7 or 8 deer they have killed with this combo, only one bullet has been recovered. Went in just behind the shoulder and ended up under the skin next to her udders. A perfect mushroom. Matt, my eldest, shot the doe during youth week a couple of weeks ago and I haven't weighed the bullet yet, but I am guessing around 85 to 95% mass retention.
As long as you don't drive them too fast, these are great bullets.
Hank