Hence why we shouldn't worry about a tactical shotgun ban. The 870 series is one of the most common "tactical" shotguns out there, let alone any sort of mod to an 1100 for some semi-auto goodness. Just no detachable magazines which I think is the real target here.
Except that the ATF study and proposal on this subject makes it clear that they don't see any difference between a detachable magazinecor a tube magazine. They also make it clear that they don't see a difference between pumps and semis either. 6-shot tube extension on an 870? According to ATF's study, that shotgun has no sporting purpose.