Could be a multitude of things, from pits in the chamber to problems with the ejector mechanism. Have it checked by a gunsmith.
It may or may not depending on if it is functioning correctly.
the shotgun takes a 2 3/4 shell
See a gunsmith.
Not sure about the 12 guage but the 16 takes 2 1/2 to 2 3/4 inch shells probably the same for 12.
You need to see a gunsmith
Many types. First, muzzle loaders do not use cartridge casings. Only autoloading firearms automatically eject a fired casing. Revolvers, and lever action, bolt action, and pump action firearms require a specific action by the shooter to eject a fired casing, as do single shot and double barreled shotguns.
Yes, if you eject it into a roaring fire.
If it's doing it regularly, it may be an extractor problem.
Possible causes include, ammunition, magazine, spring,etc..
You need the services of a gunsmith.
No...you do not have to have clip in rifle for it to eject shell casing. You can use without clip and load one bullet at a time. Alot of rifle ranges want it done that way because there is less chance of bullet remaining in chamber..good luck
Cephalopods