The.220 Swift is a semi-rimmed rifle cartridge developed by Winchester and introduced in 1935 for small game and varmint hunting. It was the first factory-loaded rifle cartridge with a muzzle velocity of over 1,200 m/s, just under Mach 4.
The velocity of the cartridge ranges from 2000 km/h (1200 mph or 550 m/s) up to about 4500 km/h (2800 mph or 1250 m/s). The Swift is a large cased .224 caliber cartridge and bullet that was created for small game such as prairie dogs, groundhogs and other vermin (or “varmints” in the US) such as marmots. When introduced it was 1,400 ft/s (430 m/s) faster than its nearest varmint-hunting competitor, which was the .22 Hornet (also .224 caliber). It was found to be an extremely accurate cartridge as well. The .220 Swift remains the fastest commercial cartridge in the world, with a published velocity of 1,422 m/s (4,665 ft/s) using a 1.9 grams (29 gr) bullet and 2.7 grams (42 gr) of 3031 powder.