<p>Different types of lead bullets were found at the archaeological site of General Paz Fort in Carlos Casares, Buenos Aires Province, Argentina. The activity at the fort dates back to 1869. The bullets found are spherical and aerodynamic and were characterized by x-ray fluorescence spectroscopy, optical microscopy and scanning electron microscopy. The analyses have reported the presence of Ca, Cu and Sn in the chemical composition of the bullets; however, because of their low concentration, they have been considered impurities. The microstructure of the bullets consisted in equiaxial grains, with an intermetallic compound CaPb₃ precipitated at the grain boundaries, due to the loss of Ca solubility during cooling after solidification. Holes and solidification fissures were also observed, indicating that the manufacturing process was by fusion and casting. One of the aerodynamic bullets is believed to have been developed by Henri-Gustave Delvigne, due to the grooves on the surface, reason by which, it has been estimated that they date back to around 1840s.</p>