Hi Tom, congrats on your acquisition. I was able to discover one a while ago and found the lover barrel to be 44/40. Has been a while since firing mine, but believe the barrel selector for the rifle cartridge is in front of the forward trigger. You will note a small lever sticks down about 1/2 inch. Does your shotgun have the flip up rear tang sight? Many times they are broken off and rather find to discover an original. Be sure and have it checked out by a competent gunsmith before firing. Bob