Is that the .17 Mach 2? If so the basic diffrence is that the .17 HMR is a .17 caliber bullet fitted to a 22 magnum casing.

The .17 Hm2 is a .17 caliber bullet fitted to a .22 long rifle casing

The mach 2 was designed to be a cheaper round than the HMR. I think people were complaining about the price of the shells for the HMR so they necked down the long rifle round to make it cheaper to shoot.

Of course the mach 2 is going to be slower because it has a lower powder charge, but it will still do basically the same thing as you would as a .22