1:8 twist barrel and fluting with a gas block from OLY. I am hoping this barrel will shoot 1/4" to 1/2" MOA if I do my part. I sure hope it does after sinking the bucks in it.
Any opinions on this SUM barrel??

Good barrel for the money from what I hear. Despite all the Oly bashing that goes on here, I've had nothing but a good experience with them. Most if not all of the complaints are from experiences that happened years ago or with cast receivers. I bought one of their MX lowers and although the tolerances were at the upper end, the finish looks great and it really does seem to be as tough as they say it is. Also, their customer service has been great with the guys on the other end of the line actually knowing what they're talking about. As long as you install it right, I'm sure it will serve you well.