The gun can be assembled. The problem is that the grip safety doesn't go all the way in. What you see in the picture is how it is even when the gun is together...it doesn't move. The gun technically fires very roughly if you pull the trigger.
This is what it looks like now:
Almost forgot:
This is what it looks like now. As far as I can tell, we're no closer to fitting than two days ago when I started. Hence why I'm skeptical it's the top ledge that needs to be filed, instead of the one on the frame.
Anyone know what exactly the ledge on the inside does? I can't tell, but it doesn't seem to do much of anything. And it's not there on the A1 frame. Another Shooter's Design quirk?