I have googled my butt off, normally I am an AK guy, but this caliber and idea has taken me by storm. I am wondering if anyone here would know where a cheap but effective upper can be acquired at? I am going to be a 5.56x45mm lower from a native Kentucky firearms maker Double Star. I really really want this caliber. Can anyone help me out. I was thinking about the Olympic arms .300 AAC/Blackout/Whisper upper for $600.00. It is currently on backorder. Any info into a good direction is helpful, thank you.