For some time after its introduction, Remington was the only factory making .41 Remington Magnum ammunition.
The same thing happened with the .44 Remington Magnum. Guns from S&W, and Ruger (to start with) ammo only from Remington, until the other ammo makers decide that (a) it will be profitable, and (b) tool up to make the ammo.
Many cartridges introduced by Remington have become "crossover" hits, now made by many, if not all major makers. Some have not, and remain Remington only products. (rifle rounds particularly).
The same thing happened with the .44 Remington Magnum. Guns from S&W, and Ruger (to start with) ammo only from Remington, until the other ammo makers decide that (a) it will be profitable, and (b) tool up to make the ammo.
Many cartridges introduced by Remington have become "crossover" hits, now made by many, if not all major makers. Some have not, and remain Remington only products. (rifle rounds particularly).