Well, first, you should ensure you can make it. You won't enlist into the Army or the Navy as a sniper - in the Army, you'd have to enlist as either an infantryman or Cavalry
…Scout, then request and be accepted for the Army's sniper course. IIRC, the only way to become a sniper in the Navy is by first becoming a SEAL. If you feel up to that challenge, by all means, go for it. I can't say with any certainty, but I believe you can enlist into the Marines for the Scout Sniper MOS. However, you still must pass the course before actually becoming a Scout Sniper. One thing you need to keep in mind is that there's a lot more to being a sniper than simply being a good shot. As for which one to choose, you need to decide what's best for you. -Bryce- Marine snipers are known for their best shot. Before you go in, you should know the basics on range cards, field sketches, moving silently in thick foilage, and other things. Knowing how to shoot a sniper (any BOLT-action rifle that can shoot past 250 yards, or a semi-auto rifle that could also shoot past 250 yards) rifle wouldn't hurt, either. Wish you the best of luck, and the choice is yours. (MORE) 
