Sorry guys I feel like I ask alot of questions, but... this one is about AR's. So I understand they are comprised of an upper and a lower which seem to be interchangeable. What are the upper and lower? Are those the only two parts that you need to have a working ar? Can you mount different caliber barrels(uppers?) on to the same lower? who makes a decent entry level m4 style AR or at least the pieces to build one? Can I start out with a decent upper and lower and add or change parts over time? Are the guns pretty accurate? Any help or explanation anyone can provide would be greatly appreciated. I have found the people on this site to be extremely helpful, knowledgeable and friendly. Thanks guys,
Caleb
Caleb