It has .052" deep rifling? (28 Ga = .550") That seems a bit excessive- but everything about it is excessive... put it next to a .410 Judge, and it makes them look tiny!
The other hurdle to pass muster as a pistol- what handgun round is it chambered for? Hard to pass it off as a pistol, when it only takes a shotgun round...
I certainly don't have any insight, and don't always assume the ATF is always correct... I was just guessing some more, in a way that doesn't involve instilling a panic-driven buying frenzy
