i have got a hold of a few ar15 lowers and i was looking to build them up and i want to get some info beforehand. i was looking at a 410 upper that was kinda cheep and thought that it would be fun. i also do not like the 223 round and was maybe going to make one a 7.62. some of the other forums that i have seen said that the 7.62 did not have a reliable mag on the market and don't like that idea. any info would be great. what are some of the ar uppers that you have used? which ones did you not like and what ones did you really like.?