Re: Considering it...
What is it that you want to do exactly? Marksman in the military equates to shooting people. It's not competitions and target practice.
So far, all I'm getting is you want to shoot people. Which is fine. Now just narrow it down. How do you want to do it? I far prefer from the view of a whirly-bird. See in that instance, when you're not shooting people you're enjoying the ride. Which beats the mess out of walking this-aways and that-aways with all your crap strapped on your back. See, my crap is back near my bed somewhere....
I suggest you decide what you want to spend the majority of your time doing. Because it won't be shooting. Of that you can be certain.
Reasons to join the military: Serving your country, getting money for college, or to get out of your nowhere town are all good and will work. Maybe you want to travel to a shitty place and hand out humanitarian aide? Or you like waiting around all day for something, you have no idea what, and you'd like to do it somewhere crappier then where you currently reside. Those are all attainable goals. If you just want to shoot people you will be sorely disappointed.