While twist, Damascus, and similarly named barrels are very old, and can be VERY dangerous to shoot; it can be done PROVIDED: A KNOWLEDGEABLE gunsmith performs a thorough check of everything. This is not a job for the local guy who replaces springs on Glocks. IF it has been blessed, then vintage-type loads from the likes of RST and Polywad are available. There are many folks who shoot Damascus barrel guns with smokeless powder and have a lot of fun. You'll not be shooting steel at ducks of 00 buck at bad guys, but a few rounds at clays.
Again, that is after a thorough check. Since competent smiths are few and far between, most folks relegate this guns to wall hangers, or ask the folks at doublegunshop.com for the name of one of those smiths with the requisite knowledge