Mossberg's new Shockwave shotgun was introduced at the SHOT Show and is finally being seen in the wild. The shotgun, classified by our friends at the BATFE as a "non-NFA firearm," features a 14-inch barrel and a 26.5-inch overall length. In short, it's a short-barrelled shotgun of a sort that doesn't require a tax stamp. Just don't conceal one about your person, in which case their determination may change (per the BATF Compliance Division letter).
Some claim the Shockwave is effectively a 5+1 capacity version of a coach gun, "ideal for home defense." Whatever the gun's utility as a home defense piece, it should nevertheless make for a potent, compact package.
Mossberg claim that it will shoot the Aguila's Minishells with an adapter, significantly increasing capacity, (and reducing recoil). The Shockwave retails for about $450.
Before you rush out and buy one, you may want to pay attention to this caveat from the Mossberg website:
NOTE: This letter only speaks to its FEDERAL status. There could be local/state laws that prohibit the sale of this gun in your state. Consult your State Police for clarification.