It does not matter what your barrel says. In order for you to safely fire 3" shotshells, the serial number on the receiver (not the barrel) must end with the letter "M". This letter indicates a "Magnum" receiver.

Otherwise, you are limited to 2-3/4" standard and 2-3/4" magnum shotshells.

If your receiver isn't built to handle 3-1/2" shells, the bolt and ejection port will be too short to properly cycle or eject empty hulls.