Caliburn - Open-top Elite Upper

My Caliburn jams a lot. That wouldn't be much of a problem with most other mag-fed blasters, except this one doesn't have much space to clear up any problems; I usually have to remove the mag, reach in with something like a screwdriver, and pry the thing out. That just won't do.

I've seen some older pictures of uppers with open spaces that would allow this, but I've had a hell of a time finding any files. So when you want something done right...