I read a little of the thread that was locked recently involving barrel break in.
Two things I'll throw my two cents in about.
First, and most surprisingly, I cannot more strongly dissagree with Armalite in regards to breaking in with moly coated bullets. I don't think anyone can argue that Mike Rock (of Rock creek barrels) has "been around the block" and is very knowledgable about the science behind ballistics and barrels. That's right....more than opinion, the man spent years upon years working for the government with funding most companies could only dream about researching ballistics and barrels and such. Rock will tell you, and show you if you are lucky enough, that repeated firing with moly bullets will ruin your barrel. Here's why in a nutshell:
Moly coats the inside of the barrel as it wears off the bullet...the copper also wears off and coats the inside of the barrel. There becomes this repeated coatings of copper/moly/copper/moly and it fuses...yes, fuses to the barrel. It becomes so hard there is no scraping or cleaning it off. Rock has seen barrels ruined in a as little as 500 rounds. Don't argue with me about this.....go talk to Mike Rock if you disagree. I'm sure even Armalite would have to admit Rock is one of the foremost authorities on barrels and ballistics. (EDIT---yes, in the short run moly bullets do shoot well but I think you'll regret it)
Second point: Tubbs final finish. I can't produce empirical data but I can say that I've seen first hand the difference in barrels both before and after. A gunsmith (one of the best in the country--as recognized by the professional industry) took a borescope and took pictures of the inside of the barrel. Any high power competitor will tell you that a barrel with a smoother and better cut rifling is going to be superior. So no, I can't provide evidence as far as group size, barrel life and such. I can only tell you it will definately smooth the bore out. Whether that improves your groups is up to you to see.