I've finally narrowed down my search for an AR upper, but I need some advice. Having a front sling swivel is a must-have. But it seems that all the uppers that come with the sling swivel have the standard AR front sight post. I'm trying to avoid this as I intend on scoping the rifle once it's put together. All the uppers without the front sight obviously have gas blocks, but none of them seem to have a mount for a swivel. All the aftermarket gas blocks that have a quad rail or low Picatinney rail run upwards of $70-80, and I'd have to buy the damned sling swivel on top of that. I find this too cost prohibitive. For those of you that have scoped your AR's, does the front sight interfere with your sight picture through the scope? Do you know of any inexpensive fixes for the gas block problem? Help!