Because the .221 Fireball doesn’t actually use .221” diameter bullets. The “221” in the cartridge title is merely a name, making it immediately distinguishable from other .22 caliber cartridges. Think about the .218 Bee, the .219 Zipper, the .220 Swift and the .225 Winchester cartridges. The name doesn’t have to relate to bullet diameter at all, since .224” diameter bullets are correct for all of these cartridges. Despite its nomenclature, the .221 Fireball requires .224” diameter bullets. Sierra offers a complete line of bullets for this
fine little cartridge.
