There's nothing wrong with the 6920, but there are also other choices. You'll read about milspec parts and that's a good thing because at least they meet some specification for quality. There are really bad parts available, also. They seem to be less frequent nowadays.
The Ruger AR is good. It's cheaper. You've read about RRA. They have a good reputation. For a few dollars more than the Colt you can buy a Daniel Defense and they also are very good. Just check on some reviews as some companies have reputations for NOT standing behind their products.
