Will heavy shot or federals heavyweights damage older shotgun barrels. When i say old i mean 36 years older
They'll both damage any barrel if the shot gets outside the wad but they should be loaded where that's not an issue. I would say you are fine as long as your barrel isn't damascus.
May want to call the manufacturer. I'd say its probably fine but then again I'm just some guy on an internet forum...
36 years sure doesn't seem that old anymore. ;)