Had someone try to demonstrate this a few decades back. About 3 times out of ten, it jammed things up big time.
IMO, ain't worth it for a measly one round....
I have not been able to make it work on my 870, but part of the reason for wanting to make it work was particularly because the 12 ga is not a measly round. They are large, powerful rounds for which the capacity of the firearm ends up being on the shy side.