Building my first AR upper right now, and my buddy has this barrel he is offering me: http://www.surplusammo.com/saa-16-1-9-m4-profile-ar-15-barrel-5-56/ He bought it a month or two ago and decided he changed his build idea, so he never even installed it. He said I could have it for $80. Seems like a good savings but this barrel has no reviews, though it claims to be their number one seller. Two quesions: Is this a decent "general use" barrel. I am not building a sniper rifler, or a combat rifle. Just a general use higher end plinker for the most part. Second, it is listed as being a "carbine length gas system" So that means if I run a A2 front sight/gas block I can only have a carbine length hang guard at the most. But if I ran a low profile gas block I could run any length free floating hand guard??