ammo is typically less than half the cost, than 17 hmr I personally am totally obsessed with the mach 2 round,
it is so quiet, with no recoil, or bbl jump, plus you can get the ammo for 5 bucks a box, 4. bucks a box of eley from
http://ammunitiontogo.com/
plus if you get a mach 2 rifle, it may also shoot the 17 aguila round, which is a 20 grain fmj solid, at about 1900 fps.
it is not as explosive as the regular m2 round, plus if you like to save skins, or sell them, it makes teeny entrance holes, and if it does exit, it is tiny as well. your mach 2 rifle may, or may not shoot the Aggie round as accurate, you just have to find out for yourself.
if you go here, you can do some comparisons for yourself,
needless to say, it is now my alltime fave round, so cool!!!
http://www.varminter.com/
http://www.varmintal.com/17hmr.htm
http://www.chuckhawks.com/index2l_rimfire.htm
with half the trajectory of a 22lr round, it has more energy, and is still going faster at 100 yds, than a 22lr is at the muzzle.