That Leupold mount looks like it attaches the same way that the B-Square mount does, by replacing the two pins in the receiver with the longer ones that secure the mount. When I had a B-Square on my 870, I found significant changes in point of impact each time that I removed and replaced the barrel. I'm talking about several inches of group movement at 100 yards. It was a concern with the high-tech sabot slug loads that I was using in my rifled barrel, but probably not so big a deal with regular slugs or buckshot.
I went to a cantilever-type mount on the barrel, and the problem went away.
John