My Model 1 upper in .223 Rem came with a Shaw barrel on it. It will shoot half inch 5 shot groups at 100 yards all the time. That means, yes, all day long. With the right ammo of course.
My .223 AI (what I am holding in my avatar) has a Shaw barrel on it and it gave me my first 700+ yard prairie dog kill. It too will shoot half inch and often less at 100 yards.
My custom .221 Fireball wears a ER Shaw barrel. I have not taken the time to work up loads for it yet but what I have shot so far have hovered around a half inch. I will play with this gun more as time goes by.
I think that ER Shaw barrels are the best bang for the buck barrels out there. I doubt that I have bought my last one.