On 2/13/2012 10:34 AM, Jim Stewart wrote:
Watching Alaska State Troopers yesterday and saw
a .410 shotgun revolver. I didn't know such a
thing existed. So this raises an interesting
point. When does a pistol firing shotgun shells
become a sawed-off shotgun? Or when does a sawed-
off shotgun become a legal pistol?

Not that Wikipedia is always authoritative, but the entry for .410 gauge
says the following:

The fact that the .410 bore shell fits in a .45 Colt chamber has
resulted in some unusual applications. While shotguns are often
limited in minimum length, a firearm chambered in .45 Colt, such
as the Contender pistol, is not defined as a shotgun even though
it can chamber shotgun shells since the barrel is rifled, not smooth.

http://en.wikipedia.org/wiki/.410_bore#Handguns