The "Army teaches you almost nothing about rifle work as is really needed, in basic. Perhaps they do a bit better if you have an infantry MOS. The Marines, last I knew, waste a lot of time teaching you silly bullseye position shooting, which is almost never used in combat. Especially the sitting and kneeling variants, when what you should be working on is snapshooting from standing. Most people need a full one second longer (to get the hit) with such shooting than is needed by a real shooter. During that one second, you are taking 4 or more shots per second from each enemy. that is not good.
While you can learn slowfire basics at NRA matches, that sort of stuff, especially the 600 yd nonsense, is almost never of any use in combat. There will be no spotter shots, there's no wind flags, theres no 20" wide, erect, stationary targets. Also there's no ear protection (probably) and such stuff takes up time and money that should be better spent on much closer, much faster, "save your life" sort of training. You need an electronic shooting timer, and when prices on ammo drop, you need a .22lr conversion unit. You need a trigger job and "glow in the dark" sights, as well as a sound suppressor, night goggles, and a laser target designator. It is dark half of the time, guys. Scopes and match peep sights are nearly worthless, at night, except on snow and in full moonlight. You need practice at hitting dodging, cover using men, from 10 to 200 yds. you need to learn to use a light on your rifle, for indoor work. you need to learn to hit from awkward firing positions, from either shoulder around cover. You need a bit of work on hitting while you move, and with one arm only, in case you are wounded or have to help a wounded buddy walk, etc. In all, you are looking at close to $10,000 to get set upw with gear and training. Are you ready to spend that much, along with about 100 hours of dedicated practice?