The .17 Remington Fireball was created in 2007 by Remington Arms Company as a response to the popular wildcat round, the .17 Mach IV. Factory loads drive a 20 grain (1.3 g) bullet around 4,000 ft/s (1,219 m/s). Velocity is close to the .17 Remington but with significantly less powder, and therefore less heat and fouling. Both are important issues to high-volume shooters such as varmint hunters.
It's based on the .221 Remington Fireball necked down to accept a .17 caliber bullet and is very similar to the .17 Mach IV. Reports on this cartridge show mild recoil, high velocity, with minimal report (noise).