There are many of us who shoot old damascus and/or fluid steel (no real difference in strength for equal quality barrels) barreled guns. There are a number of "rules" that will greatly aid your safety in shooting. I'll name as many as I can think of off hand.
1. Shoot only guns known to be still in proof or properly vetted by a gunmaker/smith of known reputation (ask further with your location and you will get recomendations).
2. Shoot only loads of known low pressure and recoil. There are good low pressure (kind to the metal parts) loads commercially available and many reloading data sets. There is no surrigate for knowing the pressure; "light load," "low brass/base," etc do not tell you anything about the loads pressure. For low recoil, keep shot charges at or below 1 oz and velocity at or below 1200 fps. Many shooters are well satisfied with 7/8 oz at 1100 fps. Black powder does not assure low pressure.
3. Most old guns have had quite a lot of shooting and, to some extent, abuse or neglect. If you are going to shoot one, plan on spending some money fixing it.
4. Read every book you can lay hands on about double guns. Dig hadoke's new book contains a very broad and deep look at modern use of older guns. Read it!!!
5. Approach this subject with great care. It is known to create addictive behaviour.
So, your gun is likely from the 1860-75 time frame. It was a properly made gun and of good quality when new. The next issue will be to determine its current condition. You need to get it to a good gunmaker/smith for evaluation. You have a hunk of family history many can only wish for. Take care to learn to shoot it properly, if it is truly shootable. Wrecking such an heirloom out of ignorance is not an option!!!
