Remington introduced the Model 591 and Model 592, along with 5mm Remington rimfire ammunition in 1970. We believed that the 5mm cartridge, with a velocity of 2105 feet per second, was superior to the .22 Win. Mag cartridge with a velocity of 1910 feet per second. Unfortunately, we were unable to convince the shooting public. Therefore, we chose to discontinue manufacturing the Model 591 and Model 592 in 1974. Manufacturing of the 5mm ammunition was discontinued in 1982.
For additional assistance you may wish to contact the following companies that specialize in older and obsolete ammunition.
Old Western Scrounger, LLC
219 Lawn St.
Martinsburg, WV 25405
RTG Sporting Collectibles, LLC
Dallas, TX 75367
Additionally, Aguilla, a Mexico based ammunition manufacturer is now producing 5mm Remington Magnum ammo. It will be marketed in the U.S. under the Centurion name.