I am trying to figure out this rail I have. I believe it is for a carbine length, the question is how far off would it be from a middy? I have a middy upper on order but I dont have anything to measure off of. As far as standard front sight placement goes, how far off am I? Basically what is the distance to front sight on carbine/middy? If I have to whack a couple inches off the top/bottom rail to acomodate that is fine.