Aren't these model 10s all "takedowns"? If that's the case, it's an awesome feature for an old reliable pump.
I have done my share of wheeling and dealing for the week, but if you still have it this weekend shoot me a note. I would love to have a look.
From what I understand, the barrel and magtube come off of the receiver with the turn of a pin.
Here is where I got that:
https://www.remington.com/sites/default/files/Model 10.pdf