The .17 HMR round is similar to rounds developed by dedicated rimfire wildcatters who worked to create a rimfire cartridge with an exceptionally flat trajectory.
These wildcatters were seeking to match the ballistics of the obsolete 5 mm Remington Rimfire Magnum, which was made from 1970 to 1974, and was to that point the fastest rimfire cartridge ever produced.
 With 5 mm diameter barrels and bullets being virtually unavailable at the time (the 5mm RMR was the last commercial 5 mm round until the 2004 release of the centerfire .204 Ruger), the commercially available .17 caliber became their bullet of choice.
 The .22 Winchester Magnum Rimfire  was the logical parent case, rather than 5mm RMR (with its unique case head size, which requires a significantly different bolt and magazine), because it was commonly available, and it is a far larger and stronger case than the next largest, the .22 Long Rifle.
 The .17 caliber wildcats not only met, but far exceeded the 5mm RMR's velocities and flat trajectory.
 The accuracy of these cartridges was also quite good.
 However, the downrange energy of the 5mm RMR is superior to both .22 WMR and .17 HMR, so there is still potential in the 5mm rimfire for wildcatters.

Hornady, in conjunction with Marlin Firearms and Sturm, Ruger (manufacturers in the rimfire rifle market), followed much the same path.
 With the .22 WMR case as the starting point, a simple barrel change was sufficient for most .22 WMR firearms to chamber the new cartridge.
 In 2002 the first rifles and ammunition began appearing on the market.
 While the ammunition was relatively expensive due to the high-performance .17 caliber bullets used, it was still cheaper than most centerfire ammunition.
 By 2004 CCI, Federal Cartridge and Remington had each introduced .17 HMR ammunition offerings.
The .17 HMR round is similar to rounds developed by dedicated rimfire wildcatters who worked to create a rimfire cartridge with an exceptionally flat trajectory. These wildcatters were seeking to match the ballistics of the obsolete 5 mm Remington Rimfire Magnum, which was made from 1970 to 1974, and was to that point the fastest rimfire cartridge ever produced.  With 5 mm diameter barrels and bullets being virtually unavailable at the time (the 5mm RMR was the last commercial 5 mm round until the 2004 release of the centerfire .204 Ruger), the commercially available .17 caliber became their bullet of choice.  The .22 Winchester Magnum Rimfire  was the logical parent case, rather than 5mm RMR (with its unique case head size, which requires a significantly different bolt and magazine), because it was commonly available, and it is a far larger and stronger case than the next largest, the .22 Long Rifle.  The .17 caliber wildcats not only met, but far exceeded the 5mm RMR's velocities and flat trajectory.  The accuracy of these cartridges was also quite good.  However, the downrange energy of the 5mm RMR is superior to both .22 WMR and .17 HMR, so there is still potential in the 5mm rimfire for wildcatters.
Hornady, in conjunction with Marlin Firearms and Sturm, Ruger (manufacturers in the rimfire rifle market), followed much the same path.  With the .22 WMR case as the starting point, a simple barrel change was sufficient for most .22 WMR firearms to chamber the new cartridge.  In 2002 the first rifles and ammunition began appearing on the market.  While the ammunition was relatively expensive due to the high-performance .17 caliber bullets used, it was still cheaper than most centerfire ammunition.  By 2004 CCI, Federal Cartridge and Remington had each introduced .17 HMR ammunition offerings.
.17 HMR