The .41 rimfire was a very low pressure black powder cartridge developed for the Remington double derringer back in the 1800's. Any gun designed for it would be blown completely apart by .41 magnum pressures. The .41 magnum is about three times as long as the .41 rimfire. Also the .41 magnum is a centerfire cartridge while the .41 rimfire is a rimfire cartridge. The two systems are incompatible.
What kind of gun do you have? It may be worth far more as a collector than a shooter. If it is a collector, any modifications to it, even if they could be made, would destroy its value as a collector.