I just traded for an S&W AR with a 7.62x39 upper. It has the 20" bbl., but, not the SS barrel like yours.
It is a lot of fun to shoot. With open sights, I was rolling a drink can at 100 yards..
I have had a few problems with FTF, but, have finally got it figured out. It doesn't like military surplus ammo, but, loves Russian Silver Bear ammo. That is real cheap, so I can have fun for a few bucks.
As I said, I really thought about the 6.8, but, am glad I went with the 7.62x39..
Hope you can make Shootzenfest, and bring that bad guy...I would love to look it over...