Interesting to hear this. However, I have tried to do as you describe. The GHF Patent of November 1877, Number 196748 shows an extension of the curved slot in the fore end plate, beyond the "keyhole". Ahead of the barrel "stud" in the barrel plate, there is a screw or stud that engages this extension. The purpose being to align the barrel stud upon assembly with the curved slot for closing. This stud or screw also prevents the barrels from swinging sideways beyond the point in opening where they should lift off.
If my barrels are swung out to the point where the swivel plate just disengages the broad recoil groove in which it moves on closing the breech, there is about 1/16 to 3/32 inches of "play" in the direction of the curved slot, of the fore end on the barrel stud. Pulling back on the fore end comes up hard on the screw or stud in the barrel plate, pushing forward simply begins to engage the curved slot and the barrels begin to close. I assume the "play" is where the shank of the barrel stud disengages its curved slot. However, I cannot lift the barrels off.
