Hi everyone. I am using the iPhone app so my search on the topic returned a ton of threads. Finding what I am looking for however is proving to be a bit like me trying to solve all of my 5th grader's word search puzzles - tedious : ( Anyway, one of the things I hope to get out of these forums is some direction in my quest to replace my A2 20" upper with a flat top A3 upper. Hopefully this will open up more options for optics. Another option I want to explore is the 300 blackout cartridge. I don't really have the opportunity to use my 20" .223/.556 barrel to its full potential. Most of the time I'm plinking cans in the desert at 50 yards and it seems like the 300 blackout might be a lot more fun. Any thoughts?