I went shooting on Saturday and the guy next to me was really interested in the barrel manufactures of my rifle. Grant had built the upper for me last year and I can no longer find the receipt. After taking the lower part of VIS I can see the N stamping on the barrel, see image link below.
http://picasaweb.google.com/isakhnov/20080908?authkey=2BEznARWWho#5251667299605938834
Looks kinda like a Noveske barrel.
GotM4 is likely correct, but to be sure, go to the front and look under the rail - peek through the vent holes. Noveske has more markings than that I think…mine does atleast.
Boltgun
I could not see any other markings there