I don't believe that measurement style would hold true for the new Taurus/Rossi .410 shotguns that have a revolving cylinder containing multiple chambers, aka a revolver.
IIRC, per the Feds, revolver bbl length is measured from the face of the cylinder to the muzzle,which can be a difference of just over 3" from the non-revolver method - plenty of room to get oneself in trouble.
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