The debate over which calibre is best for air rifle hunting has raged for yonks - and it will do forever in my opinion. Those who sit on the fence simply advocate ".177 for feather, .22 for fur".
For most of my hunting life, I've been a .22 man. I tried .177 many times, but kept preferring the extra stopping power of the .22. That was until PCP technology got so good that field accuracy became the best it's ever been since the airgun was invented (some time in the late 16th Century).
Around three years ago, I gave .177 another 'go'... and this time I switched. Indeed, I was rather dumbfounded as to why I'd never stuck with it before.
I've enjoyed three years of extra-long-range hunting with .177. (I dropped a woody at 72 yards a few months back - either a hit or total miss shot!) But where I have noticed a weakness is in the short-range stuff. Sub-30 yards.
So now, my choice comes down to range. I know that 50-yard bunnies drop to my .177 Wolf; I also know that I get too many runners at 20-ish yards. Ditto with the woodies - I often don't get to pick up despite a well-executed neck shot under 30 yards.
The .177's flatter trajectory might make hunting at long range easier, but fore close-range work, the .22's stopping power seems to have the edge for me. That's based on a lot of years' past experience.
So, I've updated the old adage for which airgun calibre is best for hunting:
Hunt with both and forget the fuss... but .177 always for