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Small shot pellets, generally classified as birdshot, were formed by the action of gravity on molten lead. The lead used in pellets was usually hardened with traces of antimony or arsenic to reduce deformation.
Small lead pellets (drop shot) were traditionally produced in a structure called a shot tower that may have measured up to ten stories tall.
The steps in this obsolete method were as follows:
- A quantity of lead was melted in a large vat at the top of the tower.
- The lead flowed into a broad shallow pan with fine holes in the bottom.
- A device struck this pan several times a second.
- Molten lead flowed as streams from holes in the stationary pan; vibration from the impact broke the streams into droplets of random size.
- During the long fall, surface tension and gravity caused the drops to become rounded.
- A tank of water at the bottom of the tower cushioned the fall, collected the pellets, and completed the cooling.
- Pellets were separated by shape (spheres produced the best shotgun patterns).
- Rejected pellets were recycled for remelting.