Just wanted to let you guys know, someone (a regular here) has a really sweet 604 upper with aftermarket 11.5" barrel on the EE right now.  Sorry no link, but on the first page. It ain't cheap, but sure is sweet. If I were doing an Air Force 630/649 (still some confusion as to correct nomenclature, but you get the point) as an SBR, I would seriously look at it as the basis for the build. Doesn't get much better these days.

Heated for ya buddy!

Yep, this one is mine.  

I've decided to go a different direction and thought someone else could use her on their SBR lower, M-16 lower or pistol lower.