The 5mm Remington Rimfire Magnum or 5mm RFM is a bottlenecked rimfire cartridge introduced by Remington Arms Company in 1969. Remington chambered it in a pair of bolt-action rifles, the Model 591 and Model 592, but this ammunition never became very popular, and the rifles were discontinued in 1974. About 52,000 rifles and 30,000 barrels for the T/C Contender pistol were sold during its brief production run. Remington discontinued the cartridge itself in 1982, leaving owners with no source of ammunition.
In 2008, the cartridge was reintroduced by Mexico's Aguila Ammunition in collaboration with Centurion Ordnance. Remington designed a completely new, bottlenecked case that was somewhat similar to the older .22 Winchester Magnum, but stronger to handle the higher pressure of the 5 mm at 33,000 PSI. From 1982 until 2008, no ammunition manufacturers manufactured rounds for this cartridge. Some firearms manufacturers even created conversion kits to allow the existing 5 mm guns to shoot other more-common cartridges.
At the 2008 SHOT Show, Aguila Ammunition announced it would reintroduce the cartridge and begin commercial production of 5mm RFM ammunition. Until 2019, the cartridges were sold in the United States of America under the Centurion brand. In 2019, Aguila Ammunition announced the company now offered two 5mm RFM loads: one with a semi-jacketed hollow point bullet and a second with a full jacketed hollow point bullet. Both loads use a 30 grain projectile and have a muzzle velocity of 2,300 fps.
