All day long. Any shotgun can handle shorter shells than it is chambered for as long as they are the same gauge.
yes it will. the rating shotguns are chambered for is the maximum size shell you can shoot. i have a 1100 LT chambered for 3 inch and i shoot 2 3/4 inch shells out of it mostly.
It will shoot any type it is chambered for.
YES IF ITS MARKED 3 INCH, THEY NEVER MADE BLACK POWDER SHELLS IN 3 INCH FOR 12 GA GUNS.
Shotguns fire shot shells. Handguns can fire specially made shotshells.
Never fire ammunition in your weapon that it is not chambered for.
With double triggers YES
Only if it is chambered for them. Have it examined by a good gunsmith
Those that are marked for 9mm ammunition. Shotguns, rifles, handguns all have been or are chambered for 9mm
Yes, shorter shells are no problem.
Definately not. I can't think of any offhand that can, but if it is not marked on the barrel then it cannot shoot them.