RE: purchased youth Elk rifle
308, good choice, in our elk camp, we consider it to be a "30-06 equivalent" and suitable for elk (and definitely for deer). Congratualtions on not going for the much recommended "underbore" stuff. BTW, we had a 14 year old girl in camp a couple years ago (about 100 pounds) who took her elk with a 30-06 with no problem.
Remington "Core-Loks" are notcommonlly recommended as a first choice for elk, most hunters up their standard to premium bullets: Nosler Partition, Barnes, Swift, etc.) "Core-Loks"are plenty good for deer all day long, elk are just different critters with different degrees of size and toughness [bones and thickness](even cow elk).
Remington "Core-Loks" are okay for practice (cheap) especially if they shoot to the.same point of impact as your good stuff. Again, they are plenty enough for deer.
[Someone here no doubt will say, "I been using "Core-Loks" for twenty years"; however, most folks go with better.]