The problem could be the ammunition. Does it date to the 70's also? Do you have another revolver in that caliber you could use to check out the ammo? Or you could obtain some other ammo.
Note that when a primer fires, the internal pressure pushes the primer metal back out and around the firing pin, giving the deep looking indent we are used to seeing. If the primer doesn't fire, there is no pressure, and no deep indent, only what appears to be a light strike.