I also have a model 11...and do not believe that they were ever chambered in 3". Check the side of the barrel close to the action, it should state 2 3/4" chamber. I also agree with fxrcleve and have experienced the same results he has and no longer soot anything lighter than #5's in my model 11. I also received mine from my grandfather and to this day it is one of my most prized possessions and shoot it every chance I get.