The shell length that the chamber can handle should be stamped on the barrell.
None. Some handguns have been made that will fire .45 Long Colt revolver rounds and .410 shotgun shells, but that does not mean that you can take any .410 shotgun and stick .45 handgun ammo in there.
Which Mossberg .410? If its the 500E, you can chamber any .410 2.5" & 3# shell. Enjoy. It's a GREAT little gun.
SORRY, you will never find any because there are none available !
It means that you have a .410 shotgun, and that the barrel has been subjected to a "proof" test. A special high pressure shell is fired during proofing that has much more energy than any shell you could buy. If the gun can safely fire that very powerful shell, it has been "proofed", and should be safe to fire with any standard shell.
The Baikal seal is the smallest species of earless seal endless to Lake Baikal in Siberia. The Baikal seal originally came to Lake Baikal hundreds of kilometers from any ocean.
There is Lake Baikal.
Sounds good but NO. Absolutely not. Shotguns are in no way built to handle the pressure a 44 cal bullet would form in the breech and barrel. The result would be catastrophic and most certainly result in a ruined firearm as well as injury and death. The .45 cal/410 deal was popularized by Taurus in it's "Judge" model which fires a 45long colt and 410 shotgun shell. Here you have a pistol designed to handle the 45 long colt pressure and therefore handle the 410 shotguns lesser pressure. Never is it a good idea to fire any ammunition in any firearm that is not clearly marked for the caliber. Never.
Sounds good but NO. Absolutely not. Shotguns are in no way built to handle the pressure a 44 cal bullet would form in the breech and barrel. The result would be catastrophic and most certainly result in a ruined firearm as well as injury and death. The .45 cal/410 deal was popularized by Taurus in it's "Judge" model which fires a 45long colt and 410 shotgun shell. Here you have a pistol designed to handle the 45 long colt pressure and therefore handle the 410 shotguns lesser pressure. Never is it a good idea to fire any ammunition in any firearm that is not clearly marked for the caliber. Never.
Any reputable gun dealer should be able to source an extension mount for the Baikal single shot rifle. Millet make mounts suitable for the Baikal rifle
Typically, no. There are some .410 shotguns which can also fire one or more rimmed pistol cartridges (usually .45 Long Colt, but I've seen them for .41 Magnum and .44 Magnum, as well), but these are purpose built to be able to do this - it cannot be done in an ordinary .410 shotgun.
There are no warm water ports any where near Lake Baikal. Lake Baikal freezes solid to depths of up to 10 metres during the Siberian winter.