I'm a RRA owner wanting to break into highpower competition; fulton armory sells a good looking competition upper with a Kreiger bbl option.  are fulton armory products good ones?  Also, is the fit to a Rock River lower fairly tight?

IMHO Fulton Armory has some of the best products out there. I believe their upper receivers are made by Cerro Fabrication. I live in MD and see them at local gunshows and all of the rifles I have seen are top notch. I purchased an M4gery from them because I didn't have any 16" barrels and have had zero problems with it. Expect to wait about a month to get the upper though. They are built to order.

You need to ask this with the guys over at the competition forum.