It’s hard to argue against the ergonomics of the AR. Few rifles are as easy to handle or operate. The safety’s location with this design is excellent, making it easy to access from either side while maintaining control at all times. Collapsible stocks make it possible for a wide variety of people to shoot an AR comfortably. The triggers are simple, with dozens of choices ranging from super-fast competition triggers to those built for tactical applications. Upper receivers of various calibers, barrel lengths and configurations can be easily changed to meet any need. There are lots of things to like, and the design has been refined and improved over the decades.
For many, the weakest point of the AR system is the buffer and the spring located in the buffer tube. Changing barrel lengths or calibers often requires these to be changed. Having that spring “boinging” in your ear can be distracting, if not outright annoying.
It can create issues with carrier tilt and other factors that effect reliability. Maybe the most limiting factor is that it makes folding stocks all but impossible without significant expense and alteration. Operating systems have improved over the years, but most long for the reliability, simplicity and robust construction of the AR’s strongest competitor, the AK-47. This has resulted in several attempts to meld the two designs. In the last few years we’ve witnessed what looks to be the best solution—an upper assembly built with AK-type internals that drops on an AR lower receiver, providing the best of both worlds.