I know less about this than you do, but I have a few thoughts to share.
First to both your questions...I don't know.
But...I have to ask. How are you going to shoot it? If you are going to shoot expensive target ammo and spend an hour getting 10 shots on paper, maybe you should consider an AR-10T with a flat-top. Scope. Target trigger.
If your going to shoot mil-surp with iron sights at 50 or 100 yards get an AR-10A2 with a chromed bore. It will last longer and your groups won't be that much bigger than what you will get with a S.S. barrel on the set-up you're talking about. It will be easier to clean and easier to sell if you decide you don't like it.
I have an A4 carbine with a 3-9X40 scope and a chrome-lined barrel.A good shooter (not me), using GOOD mil-surp ammo, could hit an orange again and again and again with my rifle at 100 yards. I usually get 10 in a row into a six inch circle at 100 yards with a wobbly bi-pod on a wobbly table.
That's all I need it to do for me. Other people have higher aspirations.
