I'm planning to buy a new heavy barrel upper assembly for my Rock River AR carbine. The purpose is to shoot heavier bullets out to 500 yards. The best price I've found is on an upper made by Vulcan. It is a 24" free floated stainless barrel with 1-8 twist. I know nothing about Vulcan except they used to make a very mean Gattling gun. Does anyone have knowledge of the quality of their small arms product?