Modern muzzleloading firearms are quite strong and safe to fire. Many years ago, firearms were made differently. Many older firearms are not safe to fire. One type of firearm that should not be fired unless it is inspected and approved is the Damascus-barreled shotgun. Take older or antique firearms to a qualified gunsmith if you are not sure if the gun is safe to fire. Don't shoot it until it has been checked!
The Damascus-barreled shotgun is easy to recognize because the way it was made resulted in fine, wavy lines which you can easily see on the barrel. Never fire Damascus-barreled shotguns or any other muzzleloader with smokeless powder.
Damascus or "damascus twist" barrels are older shotgun barrels that were typically made before 1900. Iron and steel ribbons were twisted and welded together. Damascus barrels are weaker than modern barrels and are not designed for the high gas pressures created by modern ammunition. Damascus barrels have a distinctive, irregular pattern of short, streak-like marks around the barrel.