WTB 6x45 AR-15 upper or barrel
 

I am looking for a 6x45 ar-15 barrel or upper. Preferably a 20 inch barrel with dies.

You're probably going to have to have the barrel custom cut. I had never even heard of 6x45 until I Googled it to see what you were talking about. I appears that it's still in "wildcat" status.

6mm PPC may be easier to source.