Notice how low the scope is mounted on that separate upper. I'll bet this puts the scope right at your eye with a normal cheek weld.
I have a similar upper built on an A1 upper with the handle milled off and replaced with a piece of Weaver rail. (Bought it this way at a gun show in the '80s, for IIRC $100.) I put a scope on it, low as I could get it. When I've had it at the range, I've offered other people the chance to shoulder it, without saying anything. They invariably say something like, "Wow! This thing really handles NICE! I've never handled another AR that feels as natural as this one!" The "secret" is that the stock now hits your cheek right where you want/expect it to be, unlike "normal" AR sight systems, which are too high due to the stupid charging handle, and every aftermarket system I'm aware of follows suit. How I wish someone would make an AR iron sight system that sat that low. I'd buy one immediately!
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