NEWTO36:
I would like to be more encouraging, but if your grandfather's shotgun really is in poor shape then it may not be safe to fire with any loads.
It probably needs to be looked at by a gunsmith or someone else who understands these things. Be aware that they might be reluctant to advise in the affirmative due to possible litigation if it subsequently failed and injured somebody.
The best advice, without seeing the gun, is probably to cherish it as an heirloom and a keepsake, and hang it on the wall. There are plenty of other second-hand guns out there for very little money which are sound shooters. Go grab yourself one and plaster all the small game you want, with confidence!
