First of all, I prefer gopher hunting and general plinking. Nothing can dethrone the .22 LR for plinking. It's still the first pick for that. Out to 50-75 yds, it rules.
Now, I haven't tried the hmr, so can't comment on it's ability. The price of ammo is just too high to interest me in investing in a gun. I'd rather handload 22 hornet. But, handloading with a lee loader is a bit of a pain, so I don't do that often. That's why I switched to .22 LR years ago from .22 hornet for gophers.
However, I have tried the hm2, .22 mag and .22 LR on gophers, and for me, the hm2 is at least as good or better than the .22 LR when using better ammo, like velocitors, etc. The ammo cost is the same, the range is better and the accuracy is as good or better. The .22 mag is not generally as accurate (for me, but flame on) and ammo costs more. I like it, but I definitely prefer the hm2.
To those who like to slam the hm2, try it in the gopher patch and in many cases I think you'll change your mind. It shoots much like a hopped up .22 LR, i.e. stinger, etc. Why did they invent the stinger? To do what the hm2 can do. However, I don't bother with stingers and yellowjackets anymore, since accuracy has always been abysmal.
Regarding availability, hm2 guns will become scarce in the next few years, no question. Try to find someone willing to part with a cz in hm2. SakoAlberta sells out of them fast. I'm hoping he gets some more in.
Regarding ammo availability, the 17 gr bullets are made by hornady for eley and hornady ammo, and my understanding is that these are the same 17 gr bullets used in the hmr. So, they will be available for a while based on that assumption.
To make a hm2, you need a .22 LR case and a bit of tooling to form the neck and load the bullet. Minimal tooling allows a .22LR manufacturer to produce it, which is certainly true if you can buy just the bullet from Hornady. It's about the cheapest investment possible for a manufacturer to keep making hm2 or to start up. If you couple this with the fact that hm2 is more popular in Europe than here (so I've heard), I expect that hm2 ammo will be available for some time to come, as long as someone is willing to import it. To me, only the cost of ammo in the long run can kill the hm2 in Canada, and that's why I'm stocking up. I think HM2 is slowly gaining the popularity it rightfully deserves, which is generally only among guys like myself who have decided its excellent for gophers, and actually better than the .22 LR for that, when shooting out to 100 plus yards accurately.