Remington's forgotten 5mm rimfire magnum — faster than .22 WMR and with a flatter trajectory, but discontinued after only a few years. Aguila's resurrection of the cartridge in the 2000s saved it from complete obsolescence, giving owners of Remington 591 and 592 rifles ammunition again.
Type: Rimfire
Introduced: 1970, United States
Parent case: None
Standardization: SAAMI
Bullet diameter: 0.204" (5.18 mm)
Case length: 1.02" (25.91 mm)
Overall length: 1.375" (34.93 mm)
Max pressure: 33,000 PSI
Rim type: Rimfire
Primer: Rimfire
Typical twist rate: 1:9
Muzzle velocity: 2100–2100 fps
Muzzle energy: 371–371 ft-lbs
Effective range: 150 yd
Common bullet weights: 38 gr
Primary use: Hunting, Target
Production status: Active
Also known as: 5mm RFM · 5mm Rem Rim Mag · 5mm Rimfire Magnum
History: Remington introduced the 5mm RFM in 1970 alongside the Model 591 and 592 bolt-action rifles. On paper it was impressive — a 38-grain bullet at 2,100 fps outpaced the .22 WMR significantly. In practice, Remington's market timing was poor: the rifles were expensive, the cartridge was proprietary, and the early 1970s were not prime years for rimfire innovation. Remington discontinued both the rifles…
Notable firearms: Remington Model 591, Remington Model 592
Similar cartridges: .22 WMR, .17 HMR, .17 WSM