Well, I just got off the phone with KKM to order a barrel and told them about my experience with the other barrel. They told me that the issues I had and the loose fit wasn't because of the collar, he said that made no difference? He said it was just a poorly made barrel. Anyway, there is no mistaking the difference in outward appearances and I can't help but think it did have something to do with it. Anyway, I am going to order a barrel from them. I've heard very good reports from owners who have bought the KKM for their M&P's. One thing I don't understand, they said they've been using this style of barrel for about a year now. If it didn't matter, why did they change it?