Here's the deal,

If you want to get a rifle to practice with before you enlist in the Corps, I'd recommend against a scoped bolt action rifle, or any scoped rifle for that matter. Unless you become a scout/sniper or your units designated marksman, then you will likely never shoot a rifle equipped with optics while serving in the Marine Corps (unless they change T/E weapons while you're in). The rifle that you'll become intimately familiar with (plan on sleeping with it) is the M16-A2 service rifle whice is equipped with a rear aperature (peep) sight and front sight post. On the Marine Corps KD rifle range you will be expected to hit targets with those sights from 200 to 500 yards/meters. The Corps rifle range is based on a hit or miss scoring system, because you don't hurt 'em if you don't hit them. Basically, get a bullseye, get a point, shoot white, get nothing. There is no score for a near miss. The 200 and 300 yard targets are about 20"x16" and shaped like the silouette of a man lying prone facing you (like he was trying to shoot you). The 500 yard bullseye is basically a narrow version of a waist-up human silouette without arms. So what I'm getting at is that you will be shooting at fairly small targets without the aid of a telescopic sight, which is much more difficult. A scoped rifle will not, IMO, adequately prepare you for shooting under such conditions.

Therefore, my suggestion would be to go with an M16/AR-15 clone with fixed aperature sights. You may consider getting one with a picatinny rail system on the upper receiver that will allow you to mount a detachable carry handle/rear sight assembly, but also allow you to mount a scope as well later. Naturally, this means selecting a version of the rifle with front sight assembly as well. I've also seen versions that are almost exactly like the M16-A2 minus the compensator.

Another option is this; don't buy anything and let the Marine Corps train you. That might prevent you from developing or reinforcing bad shooting habits. Some of the best marksmen I knew had never shot a rifle before entering the Corps because they learn to shoot the right way from the start. Just a thought.

Mike