Of the three (that I'm aware of) US barrel shroud, Green Mtn, or BWE, is there a "Best" choice here? I see on the GM site that it states that "WWB MAY not function in their barrel?" I like the idea that the GM barrel is chrome lined. The US barrel Shroud barrel has a lot of great reviews on their site. Original IMI barrels are way expensive. Don't know anything about the BWE barrel?