Hey, I would like to say before I start that I know nothing nothing about what I am talking about so please correct me. I would like to get rifle that is semi military. What I want: 1. A m-4 style stock with like 4 positions. 2. Fire the 223/5.56 3. Folding sights 4. Ability to add red dot + flashlight. Questions 1. If a 223 and 5.56 are the same bullet why does the barrel have to be stamped 5.56. 2. What are some of the main differences between like a Bush master/ ar-15 / ruger 556? 3. Are there a lot of options and accessorize for these guns? 4. What are somethings to keep in mind when purchasing one?