The 225 Winchester was officially announced in June 1964. Both the standard and the heavier varmint version of the Model 70 bolt action were offered for this round. The 225 replaced the older 220 Swift in the Winchester line up. It was a rimmed case with an unusually large rim for this type of cartridge. The 220 Swift never achieved great popularity and neither did its replacement, the 225. The 225 is a fine varmint cartridge with performance similar to the 224 Weatherby or the 22-250 Remington. The 225 has an edge over the 222 and 223 Remington for long range varmint shooting because the increased muzzle velocity. At one time, Winchester was supposed to furnish a 50 grain loading at 3800 fps and a 60 grain at 3500 fps, along with the standard 55 grain at 3650 fps (now reduced to 3570 fps), but these loads never materialized. For handloaders, this cartridge is nothing more than a slightly modified 30-30. Neck down a 30-30 to 22 caliber, shorten the case slightly, turn the rim to '06 dimensions and slightly improve and you have the 225 Winchester. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.