TrapperZach,
You sound like a young man who's itchin' to use that .303 Enfield! I wouldn't worry too much about finding ammo as there are allot of it around just not on every store shelf like the Dick's, Gander Mt., Cabela's, etc. I have a favorite little gunstore I frequent and he carries the stuff all the time. I'm talking about commercial brands, not mil-surplus. If you aren't 18 yrs. or older, you'll have to ask Dad to purchase your ammo for you. As you said, call around to local stores and see how you make out with the hunting loads. If that doesn't work, then just give us a shout here and we'll find some for you.
In a few more years, once you become emancipated, and call your own shots, you can get into handloading and there are allot of people locally who will help get you started correctly.
Jim