Lots more pictures of this over at Gears Of Guns. They had it listed as an AR-15, but I made the executive decision that it was an M16A1 based on its distinguishing characteristics.
Almost brings a tear to my eye to see that someone did this to an auto lower, even though it would apparently still work fine if a regular non-cutaway upper attached. Can’t really operate in extreme operations with your lower parts being that exposed though.
I love looking cutaway firearms. It really gives more of an appreciation for all the work that went into creating them.