I know the difference between the two but after a few beers one night I ended up ordering some 5.45 when I wanted 5.56 and didn't realize it until I opened up the ammo can after it was shipped to my house. So make sure you know which one you need they are not interchangeable at all.
Yes, they make some good rifles. Start a new thread if you are looking at getting a bolt gun there are more knowledgable people that me on here when it comes to shooting distance that can help you out.