Realistically, I go to the range twice a week and shoot anywhere from 50 to 200 yards when using a borrowed AR 15. When I buy/build my own I want to do the same, and also expect to clean it, put it away, and if the need ever comes - be able to grab it with confidence for home use! So I will start simple with the questions: with regards to the upper i.e. the barrel and bgc, what will I want to look for / what are the non obvious differences between chrome molly, chrome lined, stainless steal ect?????