Army infantry companies consist of three platoons, about 30-35 men in each, platoons are divided into three squads of about 10 men divided into regular grunts, a sniper, a guy with a SAW or M-60, and a grenadier or two. The heavy weapons assortment is usually delegated to a seperate company or overstrength platoon at battalion level. That's Regular Army, Reserve, and National Guard setup.
But the Rangers are entirely different animals. I don't know exactly how they set up a squad or platoon, but it would likely be similar to this or the Marine makeup.