Burrhead, that's the same basic information that appears in Cartridges Of The World. Remington adopted the .22-250 Remington caliber beginning in 1965 first in their Model 700 series rifles.
DCR, prior to 1965 what is now known as the .22-250 Remington caliber was considered a wildcat cartridge with names such as .22 Varminter and .22 Wotkyns Original Swift. Also the Remington Model 722 was manufactured from 1948-1962. This would mean the Model 722 was never offered in the .22-250 Remington caliber from the factory. Hope this helps!
Steve Mace