The process you described works when using 3 inch shells in a barrel marked for 3 inch shells installed an action originally designed for 2 3/4-inch shells. This situation is quite common since some manufacturers no longer make 2 3/4-inch replacement barrels for the shorter actions. The shell is being used in an appropriate chamber, but may not cycle in the short action.
With 3 1/2-inch shells in a 3-inch chamber it's a totally different story, you have two problems: First, the 3-inch chamber is too short to safely use a 3 1/2-inch shell. And, then there's the problem of over pressure. For 2 3/4 and 3-inch shells the SAAMI maximum average pressure (MAP) is 11.5-KSI. For the 3 1/2-inch guns the MAP has been increased more than 20%, to 14.0-KSI.