It looks more like a musket ball. The line is from the mold and the bump is called sprue or overpour.lead gets a white patina in dry acidic soil. I will post some of mine for reference.
Hey kiddo, That too is a Glen Rose Limestone fossil called a Porocystis. Round with little holes and an opening at one end. The opening has been sealed where that bump is.
My husband thought it was an algal fruiting body but it is perfectly round and the others have an indention and don't have the band around middle? The ones we have found look different kind of like olives, this one is different ? Don't know.