This is my latest project. The goal is to build a display gun that externally looks 100% convincing, but is a non-working non-gun. The starting point is an "80%" lower receiver. All the parts are mounted in the standard way, except for the fire control parts. The FCG pocket is left solid. It seems that to mount the safety/selector, all that would be needed is one transverse hole of the proper diameter. (The 80% receiver is already drilled for the safety detent and spring.) The only other externally visible parts are the trigger, and the ends of the hammer and trigger pins. To simulate the pins, I could have rings engraved on the sides of the receiver, along with the other markings. The trigger (the visible portion thereof) seems to be the biggest problem. Does anyone make a dummy trigger, which would be the finger piece on a stud which could be screwed into a drilled and tapped hole in the bottom of the receiver? The open question (to which nobody knows the answer) is how much completion is permissible before we lose the non-gun status. It seems to me that merely drilling the hole for the selector, with an otherwise solid FCG pocket, would not cross the line.