Model 12 .22 help please

[Cagle]

Im a newbie. I am just now getting into guns and have always wanted a pump .22. Well I bought a model 12 and took it out to shoot it today for the first time and the shell keeps staying in the chamber when I try to eject it. Are some .22 shells bigger in diameter than others or anything? Also I was hoping to find out what year it was the number is 734601 Thanks you, Jared

[DavidFagan]

Probably 1928, but you should also check the barrel code:= https://www.remingtonsociety.org/manufacture-dates/

All 22 rf's are the same diameter.
The first question would have to be is the gun clean?

[remington600]

Sometimes if the bore is in rough shape it builds a lot of pressure and causes the case to swell in the chamber making it too hard for the extractor to remove the case.