Hornady 17 Mach 2 Ammunition The 17 Mach 2 is also known as 17 HM2. It's a 22 Long Rifle (22 LR) necked down to 17 caliber. It shoots a 17 caliber, 17 grain bullet at about 2,100 fps. This is Hornady brand 17 Mach 2 ammunition, 50 rounds per box.
