Complete rifle product code is BCWA3S20A2X. The bold A2 denotes gov't profile and the X denotes 1/7 twist.
That is of course for the complete A3 uppered rifle. If you wanted an A2 change the first A3 to A2.
Send GI_Brat an IM and ask him about the product code for just the upper if that's all you're looking for.
If I'm wrong, I'm screwed because I'll hopefully have one delivered to my dealer tomorrow. The complete rifles are in stock as this was ordered on Monday directly from Bushmaster.