Byron, no shotgun specified Sir but, I would contact the manufacturer for advice/service for the spediest resolution.

Its not safe to shoot 3" shells in a gun with 2 3/4" chambers ....because shot shells are measured after they are fired.....meaning the petals of the crimp opening in a 3" shell don't have room to open up properly in a 2 3/4" chamber....and constricting the chamber, forcing cone and the barrel.....significantly increasing pressures.
It's not safe to do it !!
Excessive pressure has a cumulative effect. A firearm may work repeatedly without apparent issue and then one day it lets go.
Just because you can doesn't mean that you should.
Your eyes and other important body parts are mere inches from what basically becomes a pipe bomb. It only takes one time to result in a very bad day.
Best way to shoot a 3" shell get a shotgun with a 3" chamber

Byron, If it does not have a 3" chamber it will be tough. I can shoot 3" shells out of a 2 3/4" chamber shotgun. Shell husk just does not eject. Have to manually remove.