A) At the beginning of the last century most, if not all, ammunition for air-powered firearms was in the form of cup-shaped lead slugs. These were made by a number of manufacturers in various sizes – No. 1 bore (.177in), No. 2 bore (.22in) and No. 3 bore (.25in). Slugs were marketed for use in smoothbore airguns, and pellets were introduced for rifled airguns. They were not fully interchangeable, but pellets dominated the market despite being twice as expensive as slugs.
The cheaper slugs were the most popular pellet until serious target shooting with air rifles
became popular in the early 1900s. When air rifles became more sophisticated, better precision-made pellets took over the market. The cheaper form of the waisted pellet has replaced the old slug and they seem to work fairly well in smoothbore barrels.