This thread runs in a similar vein as @Ironbar's thread here. Though I've owned quite a few AR's over the years, my knowledge level doesn't extend far past basic cleaning and operation. I'd like to become more knowledgeable regarding the technical ins and outs of what makes components higher quality than others. These Black Friday sales have me thinking about building out a couple stripped lowers I have (or at least purchasing an upper or two). I'm a 'buy it once' type of guy, though I have the patience to wait for a good value. I don't want to build (or buy) an AR for the range that I wouldn't trust in a SHTF scenario when I could wait, save a bit more, and have both. For example, what makes a $250 PSA upper inferior to a $600 Colt or Daniel Defense? My only complete AR right now is a Colt 6920, which I like in it's mostly stock configuration. It'd be nice to complement it with a lightweight build (mostly for the girlfriend), and also one for distance. So, while price is admittedly one of the best indicators of quality, what other methods can be used to identify quality at a good value?