http://www.rstshells.com/store/m/2-12-Gauge.aspx
Others say 2 3/4 inch shells are acceptable but if you chose to use 2 3/4 inch shells you should be aware of the chamber pressure that they produce. I really recommend that you not exceed 9500 psi and a shot charge of 1 ounce to keep recoil energy down to protect your 125 year old wood.