As a Marine Veteran (Vietnam), former Marine Corps League Department (NJ) Shooting Competition Program Chairman, and Youth Program Leader (BSA) for several decades, I strongly urge you to allow The Corps to handle your Son's training regimen. Their basic approach is to work on the assumption that the Raw Recruit has no prior training or experience. No matter how sure you are that you can give him an edge at becoming a successful Marine, attempting to do so will effectively defeat the purpose of his recruit training experience.
The key competency he will achieve in Recruit Training will be in forging his position as an integral part of the group. This you cannot do for him and must not attempt to circumvent. It is something that Marine Recruits must achieve together.
Let us assume that you disagree and commit yourself to help him find that edge, and that you succeed. His fellow recruits will resent his superior ability, and the net consequence of your efforts will be to have alienated him from that group with which he must bond.
Young Marine Recruits are routinely given tasks at which they are intended to fail. That failure is necessary and integral to their training process. By insulating him against such failures, you do not aid his success; and could be sewing within him seeds of failures beyond those which the Recruit Training programs are prepared to resolve. In essence, you make the DI's job harder.
Allow him to enjoy his time before induction, he'll look back and wish he'd had twice as much; and he will arrive at Recruit Training Battalion in precisely the condition his Drill Instructors are best prepared to receive him.
Only The Corps can make a Marine.
Greg Langelius USMC 1966-1968
ETA 1/24/23 When I arrived at PI in 1966, I was already an NRA Junior Rimfire Rifle Expert, and had competed (I.e. earned my Team Sports letter both years) for two years on the high school's CMP team. The effect that had on my own experience in Boot Camp parallels the conjecture I make above.
