However, since velocity and the attendant flat trajectory of the .17 HMR are its main selling points, could the same bullet at a lower velocity hope to keep up saleswise? Ultimately, the success of any new cartridge depends on the number and choices of rifles in which it is offered. Since rifles in .17 Mach 2 caliber, like the .17 HMR before it, can be based on existing .22 rimfire models, the new caliber can be quickly added to a maker's catalog by the simple expedient of substituting a .17-caliber barrel. So let's not be overly surprised that Marlin's "new" Model 917 M2S looks a lot like its earlier models. This is by no means a criticism, because the 917 has a good action that has proved its worth in other Marlin rimfires.