Ok. I finally scored an AR. Way cool, but since I'm new to the AR-15 platform, I have a couple of questions. What I have is a RRA lower with a Stag M-4 upper (flat top). I was planning on mounting a scope since I can't see for shit anymore and have difficulty with iron sights. It seems that I will have to use some really tall rings to get the scope high enough to not be obstructed by the front sight. Am I crazy? What do guys do for scope mounting? Eventually, I will purchase a second upper in .204 Ruger. This style has a low profile gas block, so no problem there, but what about what I have? I like the carbine length and the 5.56 chambering as I think it makes an ideal SHTF gun, so I don't want to mod it out too much.

Second, I was wondering why the barrel reduces in diameter aprox 1.5" forward of the front sight, then continues this smaller diameter for about 1", and finally returns to full diameter the rest of the length of the barrel. I'm sure they weren't just having fun with the lathe when they built it, so I'm wondering what the purpose is? Any thoughts?

I know these are dumb ass questions, but again I'm new to AR's. I've always been a Remington #700/Savage #12/Ruger #1 kind of guy so these new-fangled semi autos are uncharted territory to me..