Smoothbore pistols are restricted in US. They are not banned, but they must be registered and a special tax must be paid when buying one.
However, there are pistols that will chamber .410 shotshells and .45LC pistol ammo. They typically have at least a short rifled section near the muzzle, or a fully rifled barrel, which allows them to be classified as regular handguns and therefore avoid the extra restrictions.
The most notable one is the Judge revolver from Taurus. There are also a few derringer-style pistols from several small manufacturers, like Cobray/Leinad.
Try Taurus
Colt has never made a 45/410 pistol
Depends on the laws where you are.
In their catalog
Yes, it is a 410/45LC combo derringer, and runs about $80-$100.
chamber length
The Taurus Judge runs about $650 MSRP
None. While there are firearms made to shoot .45 Colt AND .410 shotshells, they are designed and made to do that. A regular .410 shotgun is NOT made to do that safely.
$130.00 New in box.
Yes, one gun manufacturer at least built a two barrel derringer that was chambered for 410 rounds. While a 410 is relatively small, technically is is still a shotgun, and in a pistol as small as the derringer, firing it is a wrist-breaker.
50-400 usd
There have been several handguns made that fire .410 shotgun shells- most recently the Taurus Judge. By the way, .410 is actually a caliber of shotgun, not a gauge. A .410 shotshell is about 67 gauge- but no one uses that designation.