DRD Tactical has made a Takedown AR that can store inside a small Pelican case or backpack. It is a full length hamer forged 16″ chrome lined barrel. Mid-length gas system and comes with their Tactical QD 13″ rail. They even have a 300blk barrel that you can get for easy caliber swaps.
Tactical-life has a video review of it. There are moments without sound so bear with it.
The CDR-15 retails for $2091. Check out DRD Tactical for more info.