Shotgun Chamber Length Question

[u/Zealousideal-Let8726]

This might be a silly question, but my uncle recently gave me this shotgun and I'm not sure if it can take both 2 3/4" shells and 3" shells or only 2 3/4" shells.

The gun is:

Cooey Model 840 12GA 2 3/4" - 3 full choke Winchester proof steel Made in Canada by Winchester

I've attached a picture.

Thank you all!

[u/TopLemon3678]

You have a 3" chamber. Just don't use 3.5"