"Fastest production cartridge ever made" is a nickname that was true for the Swift for 65 years after its 1935 launch. From: .220 Swift. (2008, December 29). In Wikipedia, The Free Encyclopedia. Retrieved 18:28, March 14, 2009. from http://en.wikipedia.org
“The .220 Swift uses .224 in diameter bullets, as do most of the .22 caliber centerfire cartridges. The original prototype was based on the .250-3000 Savage case, but final designs used the 6mm Lee Navy case instead.
The Swift has the dubious privilege of being possibly the most controversial of all the many .224 in caliber cartridges and has inspired equal heights of praise and criticism. Traditionalists have roundly condemned it as an overbore "barrel burner" which can wear out a chromoly barrel in as few as 200-300 rounds, especially if long strings of shots are fired from an increasingly hot barrel. Its supporters have maintained that the fault lies with poor-quality barrel steels and the failure of users to remove copper fouling after firing, and point to instances of rifles with fine-quality stainless steel barrels chambered for the Swift, which have maintained sub-MOA accuracy after well in excess of 2,000 shots.
Performance is currently matched by the newer .223 WSSM but the Swift remains more popular. Even more popular however is the smaller, and slightly lower velocity .22-250 Remington.
The Swift remains a controversial deer caliber and its use is prohibited in many US states, and also in England, Wales and Northern Ireland for large deer such as Red, Sika and Fallow. But in some states as in Minnesota this year 2008 have backed down on their high restrictions and are letting smaller caliber rounds like the .220 swift be used to hunt deer. In the cartridge's early days during the 1930s, expert Red deer stalkers such as W.D.M. Bell, the recently retired African elephant hunter, used the .220 Swift on large stags with great success, and extolled the caliber’s seemingly magical killing powers, which they attributed to massive hydrostatic shock waves set up in the animal's body by the impact of the very high-velocity bullet.
Critics of the Swift have maintained that the light 50- or 55-grain (3.24 - 3.56g) bullet leaves inadequate margin for error in bullet placement for the average deer shooter's skills, and thus invites wounding which would have otherwise have been avoidable. There is, however, little debate about the Swift's proven effectiveness on small deer species, such as Roe, provided very fast-fragmenting "varmint"-type bullets are not used.
Most factory Swift rifles come with a fairly slow twist-rate such as 1-12" or 1-14", designed to stabilize the lighter bullets popular in varmint hunting. Custom Swifts can have faster twist-rates such as 1-9" allowing them to stabilize heavy bullets, including those with a construction suitable for larger game.
P.O. Ackley maintained that the .220 Swift was a fine round for medium-large game and used it extensively for example when culling wild burros in the American West.”