That is a fine shotgun, IMO, Damascus barreled guns are some of the most beautiful ever made. But, the bulge was most likely not caused by steel shot, but by modern shot shell propellant. Damascus steel shotgun barrels were usually made by heating and hammer forging separate pieces of wire together to form the sheet steel, and then rolled into the barrel tube. This method creates the intricate cosmetic character of the steelís appearance, but it lacks the integrity of modern mill-extruded tubing used in modern shotgun barrels. Damascus barrels usually worked fine , with the powder available in their day, but todayís modern propellants create far too much heat and pressure to be used SAFELY. If you want to hunt with this gun, have the receiver checked-out by a competent smith and consider buying a new set of modern barrels for field use. You might also consider loading your own shells with appropriate propellants & lead shot, or you can contact Westley Richards & Co., Ltd (www.westleyrichards,com
or 11(406) 586-1946) to see if they might provide you with the appropriate ammo.
Please be wise & protect yourself & this valuable firearm by not risking a very dangerous & destructive situation.
Best of luck,