The 17 HMR is much more popular than the 17 M2. I considered both a few years ago when I first started looking. I settled on the 17M2 and I have not regretted that decision. If you look at the ballistics the Mach 2 does not give up very much to its "bigger brother" but it really does save a lot in costs, especially if like me you shoot upwards of 500 rounds in a weekend. Personally I would not have a 17 HMR. The smaller round will kill gophers a long way away and they are just as accurate, perhaps even more so. You may have to look around to find an ammo supplier, so once you do buy lots! My rifle did not like the Eley/Remington round but the Hornady brand shoots very accurately indeed. My rifle is probably unique, it is a rebarrelled (by Rob McLennan) Browning A-Bolt 22 and by far and away is my favourite rifle. I would not recommend getting an auto loader (in either calibre) unless you have very deep pockets!
Jim.
Jim.