From Wikipedia:
The 5 mm Remington Rimfire Magnum is an obsolete bottlenecked rimfire cartridge introduced by Remington Arms Company in 1970. Remington chambered it in a pair of bolt-action rifles, the Model 591 and Model 592, but the round never became very popular, and the rifles were discontinued in 1974. The ammo discontinued in 1982.[2] About 52,000 rifles were sold during its brief production run.[3] As of 2008, Aguila, a Mexican ammunition company, is producing 5mm Remington Magnum ammunition.[4]
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