Almost impossible to say without having the gun in hand. The two most likely reasons are that parts are dirty, or parts are worn/broken. I would start with a thorough cleaning, with special attention to the chamber, bolt, and extractor/ejector. If that does not cure the problem. look for wear or breakage of the extractor/ejector.
12 gauge
Yes
yes the butt stocks are the same the barrels are also the same the only difference ison the 58 you need to have two holes drilled into the barrel. the holes allow the pressure to eject the shells.
I had the same gun and same problem. I found out that because it is a older model that you have to use a little more force and speed when you eject the spent shell. It should work because i have the cheapest wal-mart shells you can get and mine works just fine.
If it's a 16 gauge shotgun, the shell length is 2 3/4 inches.
Ammo, parts, dirty
Give it a thorough cleaning.
The weapon may not be a semi or an automatic one.
You need to have a gunsmith look at it.
You need to see a gunsmith.
Angle Eject
The gun needs to be stripped and cleaned, particularly the gas system. repair@countrygunsmith.net